Soft tissue balancing in articular surgery

ABSTRACT

Systems and methods may be used to perform robot-aided surgery. A system may include a robotic controller to monitor a position and orientation of an end effector coupled to an end of a robotic arm. The robotic controller may apply a force to a bone using the end effector, such as via a soft tissue balancing component. The robotic controller may determine soft tissue balance using information from a tracking system, such as a position of a first tracker affixed to the bone. The soft tissue balance may be output, such as to a display device.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.16/166,795, filed Oct. 22, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/624,621, filed Jun. 15, 2017, now issued as U.S.Pat. No. 10,136,952, which claims the benefit of priority to U.S.Provisional Applications Nos. 62/350,958, filed Jun. 16, 2016, titled“Method and System for Balancing Soft Tissue in Articular Surgery”;62/375,049, filed Aug. 15, 2016, titled “Method and System for BalancingSoft Tissue in Articular Surgery”; 62/424,732 filed Nov. 21, 2016,titled “Soft Tissue Balancing in Articular Surgery”; and 62/501,585,filed May 4, 2017, titled “Soft Tissue Balancing in Articular Surgery”,each of which is hereby incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present application relates to computer-assisted orthopedic surgeryused to assist in the placement of implants at articular surfaces ofbones.

BACKGROUND

Computer-assisted surgery has been developed in order to help a surgeonin altering bones, and in positioning and orienting implants to adesired location. Computer-assisted surgery may encompass a wide rangeof devices, including surgical navigation, pre-operative planning, andvarious robotic devices. One area where computer-assisted surgery haspotential is in orthopedic joint repair or replacement surgeries. Forexample, soft tissue balancing is an important factor in articularrepair, as an unbalance may result in joint instability. However, whenperforming orthopedic surgery on joints, soft tissue evaluations areconventionally done by hand, with the surgeon qualitatively assessingthe limits of patient's range of motion. The conventional technique mayresult in errors or lack precision.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 is a schematic view of a CAS system in accordance with someembodiments.

FIG. 2 is an exemplary perspective view of a foot support of a CASsystem in accordance with some embodiments.

FIG. 3 is a perspective schematic view of a tool head of a CAS system inaccordance with some embodiments.

FIG. 4 is a block diagram of a CAS controller used with a robotizedsurgery system in accordance with some embodiments.

FIGS. 5A-5B illustrate a robotic arm with a pin guide end effectorcomponent in accordance with some embodiments.

FIG. 6A illustrates a spike for use in a robotic soft tissue balancingsystem in accordance with some embodiments.

FIG. 6B illustrates a robotic soft tissue balancing system including aspike in accordance with some embodiments.

FIG. 7A illustrates a condyle pivot for use in a robotic soft tissuebalancing system in accordance with some embodiments.

FIG. 7B illustrates a robotic soft tissue balancing system including acondyle pivot in accordance with some embodiments.

FIG. 8 is a schematic view illustrating an intraoperative soft tissueassessment using a CAS system in knee flexion in accordance with someembodiments.

FIG. 9 is a schematic view illustrating an intraoperative soft tissueassessment using a CAS system in knee extension in accordance with someembodiments.

FIGS. 10A-10D illustrate a j-shaped adaptor and a robotic arm for use ina ligament pull system in accordance with some embodiments.

FIG. 11 illustrates a system for testing soft tissue balance inextension in accordance with some embodiments.

FIG. 12 illustrates an example user interface for displaying ligamentbalance in accordance with some embodiments.

FIG. 13 illustrates a force diagram illustrating a technique fordetermining medial and lateral forces in accordance with someembodiments.

FIG. 14 illustrates a laminar spreader advantage embodiment of a softtissue balancing test in accordance with some embodiments.

FIG. 15 illustrates a gear advantage embodiment of a soft tissuebalancing test in accordance with some embodiments.

FIG. 16 illustrates a long lever arm advantage embodiment of a softtissue balancing test in accordance with some embodiments.

FIGS. 17A and 17B are user interfaces for displaying a range-of-motion(ROM) analysis of a CAS controller in accordance with some embodiments.

FIGS. 18A and 18B are user interfaces for displaying an implantassessment of a CAS controller, enabling implant movement from a caudalviewpoint in accordance with some embodiments.

FIGS. 19A and 19B are user interfaces for displaying an implantassessment of a robotized surgery controller, enabling implant movementfrom a frontal viewpoint in accordance with some embodiments.

FIG. 20 is an example graphic-user interface (GUI) guiding a calibration(also known as a registration) of a femur for a CAS system in accordancewith some embodiments.

FIG. 21 is an example graphic-user interface (GUI) guiding a calibration(also known as a registration) of a tibia for a CAS system in accordancewith some embodiments.

FIGS. 22A-22F are example graphic-user interfaces (GUI) guiding aquantification of joint movement for a CAS system and displaying varusand valgus angles of a knee in accordance with some embodiments.

FIGS. 23A-23B are example graphic-user interfaces (GUI) for planningimplant selection and locating, and for assessing resectionintraoperatively or post-operatively in accordance with someembodiments.

FIG. 24 illustrates a tibial force detection system in accordance withsome embodiments.

FIGS. 25A-25B illustrate a patella sensor in a range of motion testingsystem in accordance with some embodiments.

FIGS. 26A-26B illustrate augmented reality systems for control of arobotic arm in accordance with some embodiments.

FIG. 27 illustrates a system for distracting a femur from a tibia inaccordance with some embodiments.

FIG. 28 illustrates a robotic arm registration system in accordance withsome embodiments.

FIG. 29 illustrates a flow chart showing a technique for using a roboticarm to perform soft tissue balancing in accordance with someembodiments.

FIG. 30 illustrates a flow chart showing a technique for using a roboticarm to perform a soft tissue pull test in accordance with someembodiments.

FIG. 31 illustrates a flow chart showing a technique for performingrobot-aided surgery using tracking in accordance with some embodiments.

FIG. 32 illustrates a flow chart showing a technique for performingrobot-aided surgery using a force sensor in accordance with someembodiments.

FIGS. 33A-33D illustrate example user interfaces for joint replacementsurgical planning in accordance with some embodiments.

DETAILED DESCRIPTION

The systems and methods described herein may be used for soft tissuebalancing using a robotic arm. A robotic arm, used during a surgicalprocedure may perform soft tissue balancing assessment. For example, acomponent (such as a pin, a cutting block, etc., as further describedbelow) may anchor to a bone and the robotic arm may be driven to pull onthe bone or other anatomy to perform the soft tissue balancingassessment. In an example, the soft tissue may be placed under tensionto determine balance. Applied tension may be determined usinginformation received from a force/torque sensor in the robotic arm. Therobotic arm may include a sensor (e.g., inertial, optical, encoder,etc.) to measure a rotation indicative of a rotation required for softtissue balancing. The soft tissue balancing may be performed with therobotic arm with a leg in flexion or in extension. In an example, acomputer-assisted surgery (CAS) system may be used to implement orcontrol the robotic arm.

In an example, a robotic arm may raise an end effector (e.g., located ata distal end of the robotic arm) to displace a femur, while the tibiaremains still by gravity, by its fixation to the table (e.g., when afoot support is used), by a human (e.g., surgical assistant or thesurgeon), by surgical tape, self-adherent wrap or tape, or other fixingdevices or components to secure the tibia. In another example, therobotic arm may use a laminar spreader to spread the bones apart. Thelaminar spreader may be inserted in the gap between the femoral condylesand the tibial plateau. In order to assist the laminar spreader,additional devices may be used and manipulated by the robotic arm. Forexample, the robotic arm may manipulate a clamp to benefit from theleveraging of the clamp to apply a greater moment of force at the bones.The laminar spreader may include a gear mechanism (e.g., planetary geardevice, rack and pinion, etc.) to assist in amplifying the force of therobotic arm.

A joint laxity may be determined using a sensor on the robotic arm or acomponent attached to the robotic arm, such as to assist in thesoft-tissue balancing at different times during a surgical procedures.For example, soft-tissue balancing may be determined prior to having therobotic arm perform an alteration to the bone, to confirm apredetermined implant size or location on the bone, or to enableadjustments to the predetermined implant size or location on the bone.In another example, the soft-tissue balancing may be determined afterone or more cut planes have been made, such as to determine whetherfurther adjustments are necessary.

Referring to the drawings and more particularly to FIG. 1, acomputer-assisted surgery (CAS) system is generally shown at 10, and isused to perform orthopedic surgery maneuvers on a patient, includingpre-operative analysis of range of motion and implant assessmentplanning, as described hereinafter. The system 10 is shown relative to apatient's knee joint in supine decubitus, but only as an example. Thesystem 10 could be used for other body parts, including non-exhaustivelyhip joint, spine, and shoulder bones. A particular function of the CASsystem 10 is assistance in planning soft tissue balancing, whereby theCAS system 10 may be used in total knee replacement surgery, to balancetension/stress in knee joint ligaments.

The CAS system 10 may be robotized, in which case it may have a robotarm 20, a foot support 30, a thigh support 40 and a CAS controller 50.The robot arm 20 is the working end of the system 10, and is used toperform bone alterations as planned by an operator or the CAS controller50 and as controlled by the CAS controller 50. The foot support 30supports the foot and lower leg of the patient, in such a way that it isonly selectively movable. The foot support 30 may be robotized in thatits movements may be controlled by the CAS controller 50. The thighsupport 40 supports the thigh and upper leg of the patient, again insuch a way that it is only selectively or optionally movable. The thighsupport 40 may optionally be robotized in that its movements may becontrolled by the CAS controller 50. The CAS controller 50 controls therobot arm 20, the foot support 30, or the thigh support 40. Moreover, asdescribed hereinafter, the CAS controller 50 may perform arange-of-motion (ROM) analysis and implant assessment in pre-operativeplanning, with or without the assistance of an operator. The CAScontroller 50 may also guide an operator through the surgical procedure,by providing intraoperative data of position and orientation and jointlaxity boundaries, as explained hereinafter. The tracking apparatus 70may be used to track the bones of the patient, and the robot arm 20 whenpresent. For example, the tracking apparatus 70 may assist in performingthe calibration of the patient bone with respect to the robot arm, forsubsequent navigation in the X, Y, Z coordinate system.

Referring to FIGS. 1 and 2, a schematic example of the robot arm 20 isprovided. The robot arm 20 may stand from a base 21, for instance in afixed relation relative to the operating-room (OR) table supporting thepatient. In one example configuration, the OR table may consist of a‘U’-shaped end portion with each side of the ‘U’ supporting a leg of thepatient and an open floor space existing between each leg. In thisconfiguration, the base is positioned in the open floor space betweenthe legs, therefore allowing the robot arm to access each leg of thepatient without repositioning the base as would be desired in abilateral total knee replacement procedure. The relative positioning ofthe robot arm 20 relative to the patient is a determinative factor inthe precision of the surgical procedure, whereby the foot support 30 andthigh support 40 may assist in keeping the operated limb fixed in theillustrated X, Y, Z coordinate system. The robot arm 20 has a pluralityof joints 22 and links 23, of any appropriate form, to support a toolhead 24 that interfaces with the patient. The arm 20 is shown being aserial mechanism, arranged for the tool head 24 to be displaceable in adesired number of degrees of freedom (DOF). For example, the robot arm20 controls 6-DOF movements of the tool head 24, i.e., X, Y, Z in thecoordinate system, and pitch, roll and yaw. Fewer or additional DOFs maybe present. For simplicity, only a generic illustration of the joints 22and links 23 is provided, but more joints of different types may bepresent to move the tool head 24 in the manner described above. Thejoints 22 are powered for the robot arm 20 to move as controlled by thecontroller 50 in the six DOFs. Therefore, the powering of the joints 22is such that the tool head 24 of the robot arm 20 may execute precisemovements, such as moving along a single direction in one translationDOF, or being restricted to moving along a plane, among possibilities.Such robot arms 20 are known, for instance as described in U.S. patentapplication Ser. No. 11/610,728, incorporated herein by reference.

Referring to FIG. 3, the tool head 24 is shown in greater detail. Thetool head 24 may have laminar spreader plates 25, actuatableindependently from a remainder of the tool head 24, for simultaneous usewith a tool support by the tool head 24. The laminar spreader plates 25are used to spread soft tissue apart to expose the operation site. Thelaminar spreader plates 25 may also be used as pincers, to graspobjects, etc. The tool head 24 may also comprise a chuck or like toolinterface, typically actuatable in rotation. In FIG. 1, the tool head 24supports a burr 26A, used to resurface a bone. In FIG. 3, the tool head24 supports a circular tool 26B. As a non-exhaustive example, othertools that may be supported by the tool head 24 include a registrationpointer, a reamer, a reciprocating saw, a retractor, depending on thenature of the surgery. The various tools may be part of a multi-mandibleconfiguration or may be interchangeable, whether with human assistance,or as an automated process. The installation of a tool in the tool head24 may then require some calibration in order to track the installedtool in the X, Y, Z coordinate system of the robot arm 20.

In order to preserve the fixed relation between the leg and thecoordinate system, and to perform controlled movements of the leg asdescribed hereinafter, a generic embodiment is shown in FIG. 1, whileone possible implementation of the foot support 30 is shown in greaterdetail in FIG. 2. The foot support 30 may be displaceable relative tothe OR table, in order to move the leg in flexion/extension (e.g., to afully extended position and to a flexed knee position), with somecontrolled lateral movements being added to the flexion/extension.Accordingly, the foot support 30 is shown as having a robotizedmechanism by which it is connected to the OR table, with sufficient DOFsto replicate the flexion/extension of the lower leg. Alternatively, thefoot support 30 could be supported by a passive mechanism, with therobot arm 20 connecting to the foot support 30 to actuate itsdisplacements in a controlled manner in the coordinate system. Themechanism of the foot support 30 may have a slider 31, moving along theOR table in the X-axis direction. Joints 32 and links 33 may also bepart of the mechanism of the foot support 30, to support a footinterface 34 receiving the patient's foot.

Referring to FIG. 2, an example of the foot interface 34 has an L-shapedbody ergonomically shaped to receive the patient's foot. In order to fixthe foot in the foot support 33, different mechanisms may be used, oneof which features an ankle clamp 35. The ankle clamp 35 surrounds therear of the foot interface 34, and laterally supports a pair ofmalleolus pads 36. The malleolus pads 36 are positioned to be oppositethe respective malleoli of the patient, and are displaceable via joints37, to be brought together and hence clamp onto the malleoli. A strap 38may also be present, to further secure the leg in the foot support 30,for example by attaching to the patient's shin. As an alternative to thearrangement of FIG. 2, a cast-like boot may be used, or a plurality ofstraps 38, provided the foot is fixed in the foot support 33. Inessence, the foot support 30 must anchor the leg to the table, withcontrollable movements being permissible under the control of thecontroller 50.

Referring to FIG. 1, the thigh support 40 may be robotized, static oradjustable passively. In the latter case, the thigh support 40 may bedisplaceable relative to the OR table, in order to be better positionedas a function of the patient's location on the table. Accordingly, thethigh support 40 is shown as including a passive mechanism, with variouslockable joints to lock the thigh support 40 in a desired position andorientation. The mechanism of the thigh support 40 may have a slider 41,moving along the OR table in the X-axis direction. Joints 42 and links43 may also be part of the mechanism of the thigh support 40, to supporta thigh bracket 44. A strap 45 may immobilize the thigh/femur in thethigh support 40. The thigh support 40 may not be necessary in someinstances. However, in the embodiment in which the range of motion isanalyzed, the fixation of the femur via the thigh support 40 may assistin isolating joint movements.

Referring to FIG. 4, the CAS controller 50 is shown in greater detailrelative to the other components of the robotized surgery system 10. Thecontroller 50 has a processor unit to control movement of the robot arm20, and of the leg support (foot support 30 and thigh support 40), whenapplicable. The robotized surgery controller 50 providescomputer-assisted surgery guidance to an operator, whether in the formof a range-of-motion (ROM) analysis or implant assessment inpre-operatively planning or during the surgical procedure. The system 10may comprise various types of interfaces, for the information to beprovided to the operator. The interfaces may be monitors or screensincluding wireless portable devices (e.g., phones, tablets), audioguidance, LED displays, among many other possibilities. For example,there is illustrated in FIGS. 20-23 and 33A-33D graphic user interfaces(GUI) e.g., 100, 110, 120, 130, and 3300A-3300D that may be operated bythe system 10. The controller 50 may then drive the robot arm 20 inperforming the surgical procedure based on the planning achievedpre-operatively. The controller 50 may do an intra-operative soft-tissuebalancing assessment, and hence enable corrective plan cuts to be made,or guide the selection of implants or other intra-operative adjustmentsto the plan. The controller 50 may also perform a post-operative ROManalysis.

The controller 50 may hence have a robot driver 51, such as when therobot arm 20 is part of the CAS system 10. The robot driver 51 is taskedwith powering or controlling the various joints of the robot arm 20,foot support 30 and thigh support 40, when applicable. As shown withbi-directional arrows in FIG. 4, there may be some force feedbackprovided by the robot arm 20 and leg support 30,40 to avoidoverextending the leg or damaging the soft tissue, and to assist indetermining joint laxity boundaries. The robot driver 51 may control thefoot support 30 in performing particular motions, to replicate aflexion/extension of the knee, with lateral movements, to measure softtissue tension and analyze the range of motion of the leg, includingvarus/valgus. As such, the robot driver 51 may output the instant angleof flexion using the position or orientation data it uses to drive themovement of the foot support 30. Sensors A are provided on the footsupport 30 or in the robot arm 20 in order to measure throughout themovement the forces indicative of the tension/stress in the joint. Thesensors A must therefore be sensitive enough to detect soft tissuetension/stress through the movement of the foot support 30. In the caseof the robot arm 20, the sensors A may be force-torque sensorsintegrated therein.

The CAS controller 50 may use a processor to implement force measurement52. Force measurement 52 may include receiving the signals from thesensors A, and calculating the instant forces in the foot support 30,representative of the tension/stress in the knee joint, or in the robotarm 20, as exemplified hereinafter. The instant forces may be used toperform ROM analysis 53 using the processor, along with the foot supporttracking data from the robot driver 51. Alternatively or additionally,the ROM analysis 53 may use tracking data received from the trackingdevice 70 to determine the range of motion of the leg, as explainedhereinafter. The ROM analysis 53 may convert the signals from thetracking device 70 into position or orientation data. In the lattercase, various types of tracking technology may be used to determine theinstant flexion/extension and varus/valgus, such as optical tracking asillustrated in FIG. 1, inertial sensors, etc. With the combined datafrom the force measurement 52 and from the robot driver 51 or othersource such as surgeon or medical professional assessment, the ROManalysis 53 may be performed. Exemplary formats of the ROM analysis 53are shown in FIG. 17B and in FIGS. 22A-22F, described hereinafter. Theinformation of the ROM analysis 53 may therefore be a pre-operativeindication of the current varus/valgus as a function offlexion/extension. The ROM analysis 53 may be performedintraoperatively, or post-operatively, to assist in quantifying the softtissue balancing during or resulting from surgery.

The processor may be used to perform an implant assessment 54 todetermine how an implant or implants will impact the range of motion.Using the ROM analysis 53, the implant assessment 54 takes intoconsideration the geometrical configuration of the implants based onselectable locations on the bone. For example, the implant assessment 54may include the bone models B from pre-operative imaging (e.g., MRI,CT-scans), whether in 3D or in multiple 2D views. The implant assessment54 may include the implant models C, such the 3D model files includingimplants of different dimensions.

The implant assessment 54 may be performed in a fully automated mannerby the processor, in evaluating from the bone model, implant models orfrom the ROM analysis 53 desired implant sizes and location on the bone(i.e., in position and orientation), to balance soft tissuetension/stress. Exemplary formats of the implant assessment are shown inFIGS. 18B, 19B and 23, described hereinafter. The information of theimplant assessment may therefore be a pre-operative or intraoperativeindication of an anticipated post-surgical varus/valgus as a function offlexion/extension.

The implant assessment 54 may optionally include operator participation.The illustrations of FIGS. 18A and 19A may be GUI items, such as in GUI130 of FIGS. 23A and 23B that may be adjusted virtually manually by anoperator, for the operator to see the impact on the graphs of FIGS. 18Band 18B, respectively. In such an embodiment, the implant assessment 54may provide the assessment to assist the operator in making a decision,as opposed to automatically proposing the desired implant sizes andlocation on the bone. The proposal of desired implant sizes and locationon the bone may be a starting point of operator navigation or decisionmaking. When the implant sizes and location on the bone is selected orset, the implant assessment 54 may produce the output D in anyappropriate format, such as GUIs 130. The format may also be that ofFIGS. 18B and 18B, providing an assessment of the proposed implant sizesand location. The output D may also include bone alteration data toassist the operator or the robot arm 20 in performing the bonealterations. In such a case, the processor may perform a resurfacingevaluation 55 to calculate the bone cut volume and location, for thebone cuts that will be made based on the implant sizes and location onthe bone.

The output D may also be a navigation file for the robot arm 20 toperform bone alterations based on the pre-operative planning from theimplant assessment 54, when the system 10 is robotized. The navigationfile may include patient-specific numerical control data defining themaneuvers to be performed by the robot arm 20 as directed by the robotdriver 51 of the system 10, or of another system 10 in an operatingroom. The navigation file for robotized surgery may incorporate acalibration subfile to calibrate the robot arm 20 and patient jointprior to commencing surgery. For example, the calibration subfile mayinclude the bone model B of the patient, for surface matching to beperformed by a registration pointer of the robot arm 20. The robot arm30 may obtain a cloud of bone landmarks of the exposed bones, toreproduce a 3D surface of the bone. The 3D surface may then be matchedto the bone model B of the patient, to set the 3D model in the X, Y, Zcoordinate system.

The use of the tracking apparatus 70 may be determinative on theinformation that will be in the navigation file C, and may providetracking data to perform the ROM analysis 53. For example, the trackingapparatus 70 may assist in performing the calibration of the patientbone with respect to the robot arm 20, for subsequent navigation in theX, Y, Z coordinate system. According to an embodiment, the trackingapparatus 70 comprises a camera that optically sees and recognizesretro-reflective references 71A, 71B, and 71B, so as to track the limbsin six DOFs, namely in position and orientation. In an embodimentfeaturing the robot arm 20, the reference 71A is on the tool head 24 ofthe robot arm 20 such that its tracking allows the controller 50 tocalculate the position or orientation of the tool head 24 and tool 26Athereon. Likewise, references 71B and 71C are fixed to the patientbones, such as the tibia for reference 71B and the femur for reference71C. As shown, the references 71 attached to the patient need not beinvasively anchored to the bone, as straps or like attachment means mayprovide sufficient grasping to prevent movement between the references71 and the bones, in spite of being attached to soft tissue. However,the references 71B and 71C could also be secured directly to the bones.Therefore, the ROM analysis 53 of the controller 50 may be continuouslyupdated to obtain a current position or orientation of the robot arm 20or patient bones in the X, Y, Z coordinate system using the data fromthe tracking apparatus 70. As an alternative to optical tracking, thetracking system 70 may consist of inertial sensors (e.g.,accelerometers, gyroscopes, etc) that produce tracking data to be usedby the controller 50 to continuously update the position or orientationof the robot arm 20. Other types of tracking technology may also beused.

The calibration may be achieved in the manner described above, with therobot arm 20 using a registration pointer on the robot arm 20, and withthe assistance of the tracking apparatus 70 when present in therobotized surgery system 10. Another calibration approach is to performradiography of the bones with the references 71 thereon, at the start ofthe surgical procedure. For example, a C-arm may be used for providingsuitable radiographic images. The images are then used for the surfacematching with the bone model B of the patient. Because of the presenceof the references 71 as fixed to the bones, the intraoperativeregistration may then not be necessary, as the tracking apparatus 70tracks the position or orientation of the bones in the X, Y, Zcoordinate system after the surface matching between X-ray and bonemodel is completed.

FIGS. 5A-5B illustrate a robotic arm 502 with a detachable pin guidecomponent 506 coupled to an end effector component 504 in accordancewith some embodiments. The detachable pin guide component 506 mayinclude one or more pins (e.g., pins 508 and 510), which may fit in oneor more apertures of the end effector component 504. The detachable pinguide component 506 may couple with the end effector component 504 in alocked position (e.g., as shown in FIG. 5A) and may be removed (e.g., asshown in FIG. 5B). The detachable pin guide component 506 may be lockedto the end effector component 504 using, for example, a screw, friction,etc. In an example, the detachable pin guide component 506 may bedisposable.

In an example, the detachable pin guide component 506 may include a cutguide (e.g., an slot for inserting a saw or other surgical instrument).For example, the detachable pin guide component 506 may include afemoral cut guide, a tibial cut guide, a 4-in-1 cut guide, or the like.In an example, the detachable pin guide component 506 may be configuredfor use with a specific implant or may be used generically.

In an example, a bushing may be used, such as between the detachable pinguide component 506 and the end effector component 504. The bushing maybe used to prevent jamming between the end effector component 504 andthe detachable pin guide component 506 or allow for easy removal of thedetachable pin guide component 506. The bushing may be removable, andmay be affixed to the end effector component 504. In another example,the end effector component may include one or more pins and thedetachable pin guide component 506 may include one or more apertures;these features may be in addition to or may replace the one or more pinsof the detachable pin guide component 506 (e.g., pins 508 or 510) or theapertures of the end effector component 504.

The detachable pin guide component 506 may include a groovecorresponding to a groove on the end effector component 504. When thedetachable pin guide component 506 and the end effector component 504are coupled, the grooves may provide an aperture for receiving a softtissue balancing component. The robotic arm 502 may apply force to thesoft tissue balancing component using the end effector component 504 orthe detachable pin guide component 506 locked to the end effectorcomponent 504. The soft tissue balancing component (e.g., as describedin further detail below, for example in the discussion of FIGS. 6A-6B,7A-7B, and 10A-10D) may apply force in turn to a bone or implantcomponent to test or configure soft tissue balance.

The soft tissue balancing component may be used to perform a ligamentbalance pull test. Based on the pull test, a femoral rotation may bedetermined. The femoral rotation may be presented (e.g., using agraphical user interface, such as those described below in thediscussion of FIGS. 22A-22F and 33A-33D). In an example, the femoralimplant rotation may be used to calculate a target femoral implantrotation. The target femoral implant rotation may be displayed (e.g.,using a user interface, such as those described below in the discussionof FIGS. 33A-33D). The target femoral implant rotation may be an inverseor opposite of the rotation of the femur rotation. For example, when thefemur rotation is 3 degrees internally, the target femoral implantrotation may be 3 degrees external from the femur. The target femoralimplant rotation may be further adjusted as well.

The femoral implant rotation may be determined such that the rotationmay compensate for an imbalance in soft tissue tension between medialand lateral compartments. The rotation of the femur during the pull testmay be directly related to the determined femoral implant rotation suchthat a rectangular or balanced gap results from applying the rotation.For example, when the rotation is applied to placement of the implant,the gap may be balanced between the medial and the lateral compartments.In an example, the robotic arm 502 may apply a force to perform the pulltest by using the soft tissue balancing component to pull on the femur.To perform the test, the robotic arm 502 may apply one or more knownloads to increase the accuracy of the determined rotation.

In an example, a torque or force sensor may be used to measure torque ofone or more of the components depicted in FIGS. 5A-5B, such as therobotic arm 502, the end effector component 504, or the detachable pinguide component 506, or on a component such as a soft tissue balancingcomponent. In an example, a sensor may be used to detect ligament stressor ligament tension. In another example, a position or orientationsensor (e.g., a navigation sensor, such as a sensor located on a portionof the robotic arm 502) may be used to determine a varus or valgus angleof a target leg. The varus or valgus angle may be used to determineligament pulling in the target leg. From the varus or valgus angle orthe stress or tension on the ligament, pulling on the soft tissue may bedetermined and a rotation to correct the pulling may be determined, andmay be output on a graphical user interface (GUI), such as thatdescribed with respect to FIGS. 33A-33D.

In an example, a ligament test or other soft tissue balancing test maybe performed before a bone resection cut is performed. For example, thesoft tissue balancing test may be performed before any resection of afemur or a tibia. In an example, the soft tissue balancing test may beperformed after resection and implantation of an implant to verify thatthe soft tissue is correctly balanced. For example, a first test may beperformed pre-resection, which may result in a rotation angle to be usedfor balancing, and a second test may be performed after the implant isinserted to verify that the rotation angle was correct or that theimplant was properly seated.

In an example, resecting a bone may include using the robotic arm 502.The robotic arm 502 may have a cut guide attached to the end effectorcomponent 504 to guide the resection. A guide may be used to align acutting, burring, or sawing device with a target object, such as atarget bone. Cut guides are often manually placed by a surgeon on thetarget object. In other examples, cuts are made using fully autonomousrobotic cutting devices. In another example, a surgeon may guide therobotic arm 502 collaboratively with force assistance from the roboticarm 502 (e.g., using a force sensor coupled to the robotic arm 502). Inthis example, the surgeon may apply a small directional force while therobotic arm 502 moves in response. The robotic arm 502 may thenautomatically align to a cut plane in response to a surgeon selection(e.g., on the robotic arm 502 or on a user interface). In an example,the cut guide may be used to precisely align a surgical instrument tomake a cut, such as on a target bone or other target object. Thealignment of the end effector component 504 may involve a planningsystem with a user interface including positioning a representation ofthe end effector component 504 on a representation of the target object.During the surgical procedure, a selectable indication on anintraoperative user interface (e.g., those of FIGS. 33A-33D) may be usedto activate movement the end effector component 504 to the plannedalignment position. The cut guide may be used as a guide for thesurgical instrument to make a cut on the target object, such as to alignthe surgical instrument with a specific plane or line. By using a cutguide, a surgeon may retain control of the surgical instrument whilealso using the robotic arm 502 to ensure that the surgical instrument isaligned with a predetermined cut plane or cut line. The robot inconjunction with a surgical navigation system allows for repeatabletransfer of pre-defined surgical plan to the patient during the surgicalprocedure, while still allowing the surgeon some level of control overthe final cuts.

FIG. 6A illustrates a soft tissue balancing component, including a spike602 for use in a robotic soft tissue balancing system 600A in accordancewith some embodiments. The spike 602 may be used as a femoral spike toapply force to a femur. The spike 602 may include a shaft portion 603 toreceive force and transfer the force via rigidity of the spike 602 to aspike portion 607, which in turn may apply force on the femur. The spike602 may include a hollow shaft defined by an outer shaft wall 605. Thehollow shaft may be perpendicular to the shaft portion 603. The hollowshaft may be used to lock or secure the spike in place (e.g., to preventrotation), such as relative to a robotic arm or component.

In an example, the spike portion 607 of the spike 602 may include anenlarged surface area to minimize bone damage. In an example, differentshaped spikes may be used (e.g., flat, rectangular, triangular, round,etc.), such as to accommodate the patella or soft tissue. In an example,the shaft portion 603 of the spike 602 and a component used to secure orcouple with the spike 602 (e.g., a robotic arm or components attachedthereto) may have a combined thickness, average thickness, or maximumthickness similar to (e.g., within a tolerance of) or less than afemoral implant to be used. For example, the shaft portion 603 of thespike 602 and the component used to secure or couple with the spike 602may have a size such that a patellar tendon is under natural tensionwhen the spike 602 is used to apply force to the femur.

FIG. 6B illustrates a robotic soft tissue balancing system 600Bincluding the spike 602 in accordance with some embodiments. The softtissue balancing system 600B includes a robotic arm 604 to apply a forceto the spike 602. The spike 602 may apply the force to a femur 606. Therobotic arm 604 may include an end effector component 610 and a pinguide component 608, which may be detachable. The robotic arm 604, endeffector component 610, and pin guide component 608 may be thosedescribed above with respect to FIGS. 5A-5B. In an example, the pinguide component 608 attaches to the end effector component 610 to securethe spike 602 in place relative to the robotic arm 604. The pin guidecomponent 608 may be decoupled from the end effector component 610 toallow for removal of the spike 602.

A force applied by the robotic arm 604 on the spike 602 may cause thefemur 606 to move, putting ligaments in tension. As the ligaments arepulled by the force on the femur 606, a balancing test may be performed.For example, tension in the ligaments may be measured or observed, forceon the femur 606 may be tracked, or a rotation angle may be determinedor observed. The rotation angle may then be used to set a target femoralrotation.

In an example, arrow 612 may represent a pull direction (e.g., forcedirection) that the spike 602 pulls the femur 606. For example, thearrow 612 may point along a line parallel to a plane of a resection cutof the femur 606. In an example, the arrow 612 may point along a lineperpendicular to a plane formed by a top surface of the pin guidecomponent 608 or perpendicular to an axis of the spike 602.

FIG. 7A illustrates a soft tissue balancing component, including acondyle pivot 702 for use in a robotic soft tissue balancing system 700Ain accordance with some embodiments. The condyle pivot 702 may be usedto apply force to a femur. The condyle pivot 702 may include a shaftportion 703 to receive force and transfer the force via rigidity of thecondyle pivot 702 to platform arms 705A-705B, which in turn may applyforce on the femur. The condyle pivot 702 may include a hollow shaft,which may be perpendicular to the shaft portion 703. The hollow shaftmay be used to lock or secure the condyle pivot in place (e.g., toprevent rotation), such as relative to a robotic arm or component.

In an example, the platform arms 705A-705B of the condyle pivot 702 mayinclude enlarged surface areas to minimize bone damage. In an example,different shaped platform arms 705A-705B may be used (e.g., flat,rectangular, triangular, round, etc.). In an example, the shaft portion703 of the condyle pivot 702 and a component used to secure or couplewith the condyle pivot 702 (e.g., a robotic arm or components attachedthereto) may have a combined thickness, average thickness, or maximumthickness similar to (e.g., within a tolerance of) or less than afemoral implant to be used. For example, the shaft portion 703 of thecondyle pivot 702 and the component used to secure or couple with thecondyle pivot 702 may have a size such that a patellar tendon is undernatural tension when the condyle pivot 702 is used to apply force to thefemur.

The platform arms 705A-705B may each apply a same force or may applydifferent forces. For example, a torque may be applied to the condylepivot 702 by the robotic arm 704 to keep the platform arms 705A-705Baligned along a plane, which may include varying force between theplatform arms 705A-705B. When a limit is reached, for example, a firstligament is put in tension at a threshold level or a threshold force isreached, the relative forces applied on the platform arms 705A-705B maybe used to determine a rotation angle to be used when resecting thefemur 706 or when creating or inserting an implant. In another example,the platform arms 705A-705B may have equal force applied to each, and beallowed to rotate (e.g., away from an initial plane). The angle of theplatform arms 705A-705B (e.g., relative to the initial plane) at an endposition may be used to determine the rotation angle for later use. Theend position may be determined when a threshold tension is reached onligaments (e.g., a medial and a lateral ligament), when a thresholdforce is reached, or when a predetermined distance is reached (e.g., 5mm, 10 mm, a distance corresponding to a tibia implant thickness such as10 mm, 11 mm, 12 mm, etc.), which may include a safety factor (e.g.,+/−1-5 mm), or the like. In an example, a combination of end positionmarkers may be used, such as a predetermined distance approximatelyequal to a tibia implant thickness (e.g., an insert (poly) or an implantassembly, which may be predetermined using planning techniques), whileretaining a maximum force as safety factor. For example, when a maximumforce is reached before the predetermined distance, the robotic arm maybe stopped. In another example, balanced ligaments may be used to markthe end position. The threshold tension may be determined visually orusing a sensor. The end position (e.g., when rotation stops) may bedetermined by optical navigation in an example.

FIG. 7B illustrates a robotic soft tissue balancing system 700Bincluding the condyle pivot 702 in accordance with some embodiments. Thesoft tissue balancing system 700B includes a robotic arm 704 to apply aforce to the condyle pivot 702. The condyle pivot 702 may apply theforce to a femur 706, such as by pushing the femur 706 in a directionaway from a tibia. For example, the condyle pivot 702 may use theplatform arms 705A-705B to push on the femur 706 to apply the force. Therobotic arm 704 may include an end effector component 710 and a pinguide component 708, which may be detachable. The robotic arm 704, endeffector component 710, and pin guide component 708 may be thosedescribed above with respect to FIGS. 5A-5B. In an example, the pinguide component 708 attaches to the end effector component 710 to securethe condyle pivot 702 in place relative to the robotic arm 704. The pinguide component 708 may be decoupled from the end effector component 710to allow for removal of the condyle pivot 702.

A force applied by the robotic arm 704 on the condyle pivot 702 maycause the femur 706 to move, putting ligaments in tension. As theligaments are pulled by the force on the femur 706, a balancing test maybe performed. For example, tension in the ligaments may be measured orobserved, force on the femur 706 may be tracked, or a rotation angle maybe determined or observed.

In an example, a pivot point of the platform arms 705A-705B may be atthe shaft portion 703 of the condyle pivot 702. The shaft portion 703may be aligned, using the robotic arm 704, at various points of thefemur 706. For example, the pivot point may be located at a medialcondyle in a varus knee. In another example, pivot point may be thecenter of the knee. In yet another example, instead of using a spike asin FIGS. 6A-6B or a condyle pivot as in FIGS. 7A-7B, a posterior paddle,c-shaped adaptor, or other shape may be used to apply force to the femur706.

In an example, a device may be inserted into a joint, such that turninga screw of the device may allow the soft tissue balancing test to beperformed. For example, the device may expand at the turn of the screw.In an example, the robotic arm 704 may turn the screw. In an example, aforce sensor for detecting force on the tibia, on the femur, or betweenthe tibia and the femur may be the eLIBRA soft tissue force sensordevice from Zimmer Biomet of Warsaw, Ind.

The example device illustrated in FIGS. 7A and 7B is shown contacting acertain portion of a distal end of a partially resected femur. This isan exemplary engagement with the distal end of the femur, other examplesmay engage the femur in a different orientation or before or afterresections. Additionally, in some examples, the platform arms 705A-705Bmay be contoured to facilitate engagement with the target bone surface.

In an example, arrow 712 may represent a pull direction (e.g., forcedirection) that the condyle pivot 702 pulls the femur 706. For example,the arrow 712 may point along a line parallel to a plane of a resectioncut of the femur 706. In an example, the arrow 712 may point along aline perpendicular to a plane formed by a surface of the pin guidecomponent 708 or a surface of the condyle pivot 702, for example asurface in contact with the femur 706.

In an embodiment, the CAS controller 50 may operate the robot arm 20 toperform a robotized soft-tissue balancing assessment, such as by using aprocessor to perform soft-tissue balancing 56, although it may also bedone without robotized assistance. Referring to FIG. 8, with a device 80anchored to the bone (such as a pin, a cutting block, etc.), the robotarm 20 may be driven to pull on the bone and hence put the soft tissueunder tension. Applied tension may be controlled using the signals fromthe force-torque sensors A in the robot arm 20 with the output of theforce measurement 52. In an embodiment, the device 80 includes a pin anda cutting block. The robot arm 20 may pull the femur away from the tibiaby manipulating the pin of the device 80, such that the pin (and femur)may rotate relative to the robot arm 20. The rotation of the femur willnaturally go toward soft tissue balancing, in which tension T1 is equalto tension T2. The device 80 may further include an inertial sensor tomeasure a rotation θ indicative of the rotation required for soft tissuebalancing. The rotation θ may also be monitored and measured by therobot arm 20, with appropriate sensors (optical, encoders, inertial,etc). Referring to FIG. 9, similar operations may be performed with theleg being in extension. FIG. 9 is a schematic view illustrating anintraoperative soft tissue assessment using a CAS system in kneeextension in accordance with some embodiments. In an example, the robotarm 20 may pull the femur away from the tibia, either in extension or inflexion, and automatically stop. The robot arm 20 may stop for exampleat a predetermined distance (gap), when a threshold force or tension isreached, or at a user-selected stopping position. The predetermineddistance (e.g., 5 mm, 10 mm, a distance corresponding to a tibia implantthickness such as 10 mm, 11 mm, 12 mm, etc.), may include a safetyfactor (e.g., +/−1-5 mm), or the like. In an example, a combination ofend position markers may be used, such as a predetermined distanceapproximately equal to a tibia implant thickness (e.g., an insert (poly)or the implant assembly, which may be predetermined using planningtechniques), while retaining a maximum force as safety factor. Forexample, when a maximum force is reached before the predetermineddistance, the robotic arm may be stopped. In another example, balancedligaments may be used to mark the end position.

In FIG. 8, the soft tissue is put under tension using the robot arm 20acting on the device 80. In an embodiment, the robot arm 20 raises thedevice 80 to displace the femur, while the tibia remains still bygravity or by its fixation to the table (e.g., when a foot support 30 isused), by a human (e.g., surgical assistant or the surgeon), by surgicaltape, self-adherent wrap or tape, or other fixing devices or componentsto secure the tibia. It is also considered to use the laminar spreaders25 of the robot arm 20, as in FIG. 3, to spread the bones apart. Thelaminar spreaders 25 may be inserted in the gap between the femoralcondyles and the tibial plateau. In order to assist the laminarspreaders 25, additional devices may be used and manipulated by therobot arm. For example, the spreaders 25 may manipulate a clamp tobenefit from the leveraging of the clamp to apply a greater moment atthe bones. Likewise, the spreaders 25 may manipulate a spreader withgear mechanism (planetary gear device, rack and pinion, etc), to assistin amplifying the force of the robot arm.

The processor may perform soft-tissue balancing 56 to quantify jointlaxity to assist in the soft-tissue balancing at different momentsduring the surgical procedures operated by the CAS controller 50. Forexample, the soft-tissue balancing 56 may assess soft-tissue balancingprior to having the robot arm 20 perform the alterations to the bone, toconfirm the desired implant sizes and location on the bone produced bythe implant assessment 54, or to enable adjustments to the desiredimplant sizes and location on the bone, and impact the output of theresurfacing evaluator 55. The soft-tissue balancing 56 may assesssoft-tissue after cut planes have been made, to determine whetherfurther adjustments are necessary.

In another embodiment, the output D is in the form of a patient-specificcut guide 3D file, for a patient-specific cut guide to be machined or 3Dprinted for operative use. For example, the patient-specific cut guidemay have negative surfaces of the bone model for unique positioning onthe bone, such that cut planes and drill guides are placed as planned.As another example, the output D may be a navigation file, of the typeprogrammed into inertial sensor units manually navigated by an operator.Referring to FIG. 9, similar operations may be performed with the legbeing in extension.

In an example, the soft tissue assessment may be performed with the legin flexion (e.g., as shown in FIG. 8) or in extension (e.g., as shown inFIG. 9). When in flexion, the leg may be held at a 90 degrees angle offlexion, or substantially 90 degrees, such as within plus or minus tendegrees. In another example, with the leg in extension, the leg may beheld at zero degrees angle of extension, 10 degrees, 20 degrees, or thelike, such as based on surgeon preference. The soft tissue assessmentmay be used to measure or display gap measurements for soft tissuebalancing during a test when a knee is in flexion or extension. In anexample, the soft tissue balancing assessment when the knee is inflexion may include not releasing the femur when pulling. In anotherexample, the test may include pulling on the femur, then measuring anamount of rotation that results in balance between the soft tissue(e.g., ligaments). The femur may be free to rotate to find the balancebased on the amount of force on the ligaments. In an example, the softtissue balancing assessment may be performed with the patella in placeor dislocated.

FIGS. 10A-10D illustrate a soft tissue balancing component, including aj-shaped adaptor 1006 and a robotic arm 1002 for use in a ligament pullsystem (shown in views 1000A-1000D) in accordance with some embodiments.The j-shaped adaptor 1006 may attach to an end effector 1004 on a distalend of the robotic arm 1002. In an example, the end effector 1004 may beconfigured to receive the j-shaped adaptor 1006 and lock the j-shapedadaptor 1006 into place, secured to the robotic arm 1002. The attachmentof the j-shaped adaptor 1006 to the end effector 1004 may result in anaudible click. View 1000A illustrates the j-shaped adaptor 1006 detachedfrom the end effector 1004 and view 1000B illustrates the j-shapedadaptor 1006 coupled to the end effector 1004. View 1000C illustratesthe j-shaped adaptor 1006 attached to the end effector 1004 in aconfiguration for performing a soft tissue balancing test on a lateralportion of a femur and view 1000D illustrates the j-shaped adaptor 1006attached to the end effector 1004 in a configuration for performing asoft tissue balancing test on a medial portion of a femur. In anotherexample, the j-shaped adaptor 1006 may be configured to be reversibleand lock into the end effector 1004 at the same place in each direction,or in four directions (e.g., perpendicular to the lateral or medialviews). In an example, the robotic arm 1002 may apply a force to thej-shaped adaptor 1006 to pull the j-shaped adaptor 1006 in a directionwhile the j-shaped adaptor 1006 is engaged with a femur. Pulling on thefemur may allow the ligament pull system to determine a rotation anglefor balancing the ligaments of the knee. In an example, the j-shapedadaptor 1006 may be used to pull on the femur with the patella of theknee in place. In an example, the patella or soft tissue may be avertedor in a normal position when doing the pull test in flexion.

A bone spike may be used to secure the j-shaped adaptor 1006 to a bone.For example, the bone spike may be placed by a surgeon or using therobotic arm 1002 at a predetermined location on the bone. The j-shapedadaptor 1006 may be fitted around the spike with a spike adaptor anchorlocated at a distal end of the j-shaped adaptor 1006. The j-shapedadaptor 1006 may be fitted around the spike using the robotic arm 1002,such as automatically, or using force sensing and surgeon input. Thej-shaped adaptor 1006 may then be used to apply a force on the bone(e.g., the femur) to pull the bone away form a second bone (e.g., thetibia) to conduct a soft tissue balancing test. The robotic arm 1002 mayapply the force on the j-shaped adaptor 1006, which then in turn appliesthe force on the bone spike, which then applies the force on the bone.The soft tissue balancing test may be performed with the patella or softtissue in place (e.g., not dislocated) by using the j-shaped adaptor1006 to avoid the patella or soft tissue. For example, the j-shapedadaptor 1006 may reach around the patella, but remain rigid when theforce is applied on the j-shaped adaptor 1006 by the robotic arm 1002,thus pulling the bone (e.g., the femur), while avoiding the patella. Astraight component adaptor used instead of the j-shaped adaptor 1006 maybe interfered with by the patella and require dislocation of thepatella. Performing the soft tissue balancing test with the patella inplace may result in more accurate results than performing the softtissue balancing test with the patella dislocated.

In an example, the robotic arm 1002 may apply a force on the j-shapedadaptor 1006 to cause the j-shaped adaptor 1006 to pull on the bonespike until a threshold force is reached, a threshold tension in thesoft tissue is reached, according to a preoperative plan, a surgeonstops the procedure, a predetermined distance is reached, or the like.The predetermined distance (e.g., 5 mm, 10 mm, a distance correspondingto a tibia implant thickness such as 10 mm, 11 mm, 12 mm, etc.), mayinclude a safety factor (e.g., +/−1-5 mm), or the like. In an example, acombination of end position markers may be used, such as a predetermineddistance approximately equal to a tibia implant thickness (e.g.,predetermined using planning techniques), while retaining a maximumforce as safety factor. For example, when a maximum force is reachedbefore the predetermined distance, the robotic arm may be stopped. Inanother example, balanced ligaments may be used to mark the endposition. The j-shaped adaptor 1006 may pull on the bone spike until adistance matching a preoperatively or intraoperatively known thicknessof a tibial implant is reached. When the j-shaped adaptor 1006 completespulling, an angle of rotation of the bone may be recorded (e.g., bysurgical planning software, a robotic controller, etc.) for later pinpositioning or cut guide placement. In an example, the j-shaped adaptor1006 may include a horseshoe-shaped adapter (i.e., two j-shaped adaptorsconnected at their distal ends).

FIG. 11 illustrates a system 1100 for testing soft tissue balance inextension in accordance with some embodiments. The system 1100 may beused to measure or display gap measurements for soft tissue balancingduring a test when a knee is in extension. For example, an extension gaptest may include pulling on a tibia while a knee is in extension. In anexample, a spacer block may be placed on a jig 1102, for example withshims or other flat thin surface inserted as the spacer block. Forexample, a flat attachment may be slid on the jig 1102 to perform thetest. The jig 1102 may be attached to a robotic arm 1104, which maycause a force to be imparted onto the flat attachment via the jig 1102.The force may be imparted onto the tibia to pull the tibia away from thefemur. In an example, the flat attachment may include one or more feetthat may clip into a slot of the jig 1102. The jig 1102 may be used toassess the extension gap and to test varus/valgus angles. In an example,the soft tissue balancing test may be performed at a specifiedvarus/valgus angle. Releases may be performed at that angle until theligaments are balanced. The ligament balancing may be performed bymeasuring tension (e.g., by measuring force) within a component, such asusing a sensor.

In another example, the soft tissue balancing test when the knee is inextension may include using a plate fixed to the tibia to pull on thetibia. The torque may be measured (e.g., using a sensor) to determine anamount of imbalance. In an example, the test may be performed by a platethat is free to rotate. The free rotation plate may be used to applyforce on the tibia until the varus/valgus angles are zero to find abalance. In an example, the jig 1102 may include a spacer block. Thespacer block may widen to apply tension to perform a ligament balancetest.

FIG. 12 illustrates an example user interface 1200 for displayingligament balance in accordance with some embodiments. The user interface1200 includes a medial tension indication 1202 and a lateral tensionindication 1204. In the example shown in user interface 1200, the medialtension represented in indication 1202 is less than the lateral tensionrepresented in indication 1204. This indicates that the lateral tensionshould be decreased, such as by performing a release on the lateralligaments. In an example, lateral tension may include tension betweencompartments, such as lateral and medial compartments, or collateralligaments (e.g., medial and lateral collateral ligaments) as an exampleto differentiate the medial and lateral sides. In another example, allligament complexes play a role in the balance of the knee, and thus maybe balanced. The ligaments may include a medial collateral ligament(MCL), a lateral collateral ligament (LCL), a posterior cruciateligament (PCL), posterior capsule, etc.

In an example, the difference displayed in the user interface 1200between the two ligaments may include a difference in force, adifference in torque, or a difference in displacement between the twoligaments. As releases are performed, the user interface 1200 may beupdated in real time to display updated differences. For example, arelease may be performed on the lateral ligament in the example shownfor user interface 1200, which may cause the balance between the medialand lateral ligaments to become closer to even. In an example, a roboticarm may apply a constant force on a bone to allow a surgeon to performthe ligament releases while watching the extension ligament balance inreal time. In another example, a robotic arm may be used to perform theligament releases. The process may be iterated until the ligamentbalance is achieved.

FIG. 13 illustrates a force diagram 1300 illustrating a technique fordetermining medial and lateral forces in accordance with someembodiments. The force diagram 1300 illustrates measurements of forcesacted on a tibia 1302 by an end effector 1304 of a robotic arm 1306during a soft tissue balancing test. In an example, a robotic forceF_(RBT) is applied by the end effector 1304 on the tibia 1302. Oppositeforces are applied by the tibia 1302, which may be effectively labeled amedial force F_(MCL) and a lateral force F_(LCL). The forces arebalanced according to Eq. 1 below:

F _(MCL) +F _(LCL) =F _(RBT)   Eq. 1

The moment of force (or torque) applied by the robotic arm 1306 may beknown using a force or torque sensor, such as between the end effector1304 and the robotic arm 1306. The moment may be labeled M_(RBT) and maybe balanced by moments of equal and opposite torque at medial andlateral distances (labeled L_(MCL) and L_(LCL)) from the M_(RBT) momentto the medial force and the lateral force according to Eq. 2 below:

F _(MCL) ·l _(MCL) +F _(LCL) ·l _(LCL) =M _(RBT)   Eq. 2

The lateral and medial distances may be known using a tracking system,such as an optical tracking system, using known dimensions of the endeffector, or using sensors attached to components of the system. Usingthe known F_(RBT) and M_(RBT) and the known distances, Eqs. 1 and 2 maybe solved for the F_(MCL) and the F_(LCL). These two forces may be usedto determine balance in soft tissue, such as the medial collateralligament and the lateral collateral ligament. The two forces may beoutput on a display device or user interface, such as those shown inFIGS. 22A-22F or 33A-33D below or FIG. 12 above.

FIG. 14 illustrates a laminar spreader advantage embodiment 1400 of asoft tissue balancing test in accordance with some embodiments. FIG. 15illustrates a gear advantage embodiment 1500 of a soft tissue balancingtest in accordance with some embodiments. FIG. 16 illustrates a longlever arm advantage embodiment 1600 of a soft tissue balancing test inaccordance with some embodiments. In some cases, a robotic arm may notbe able to apply sufficient force to separate the femur and tibia orperform a soft tissue balancing test. To increase the force applied bythe robotic arm, a mechanical advantage may be used. For example, thelaminar spreader advantage embodiment 1400 illustrates a laminarspreader 1408 to apply additional support while the robotic arm 1406applies a force at 1410 (e.g., using a bone spike as described herein)on a femur 1402 to separate the femur 1402 from a tibia 1404. In theexample shown in FIG. 14, force may be applied to the laminar spreader1408 by a surgeon (or surgical assistant) or by another robotic arm.

In the example shown in FIG. 15, the gear advantage embodiment 1500 usesa robotic arm 1502 affixed to a gear 1504 to apply a torque on a secondgear 1506 to move a pivot joint 1508 to cause a first spreader arm 1510to separate from a second spreader arm 1512, the first spreader arm 1510applying a force on a first bone and the second spreader arm 1512applying a force on a second bone. The gear advantage embodiment 1500relies on the additional torque of the gears 1504 and 1506 to increasethe output force of the robotic arm 1502. In the example shown in FIG.16, a robotic arm applies force to a laminar spreader 1602 with longlever arms to separate a femur 1604 from a tibia 1606. The torqueapplied by the robotic arm is increased via the long lever arms.

FIGS. 17A and 17B are user interfaces for displaying a range-of-motion(ROM) analysis of a CAS controller in accordance with some embodiments.FIGS. 18A and 18B are user interfaces for displaying an implantassessment of a CAS controller, enabling implant movement from a caudalviewpoint in accordance with some embodiments. FIGS. 19A and 19B areuser interfaces for displaying an implant assessment of a robotizedsurgery controller, enabling implant movement from a frontal viewpointin accordance with some embodiments.

Referring to FIG. 17B, a graph illustrating an actual varus/valgusbalanced line 60 as a function of the leg extension is shown, as aresult of the controlled movements of the foot support 30. The forcemeasurement data allows the positioning of 60, as an indication of thevarus/valgus value at balanced soft tissue. Lines 61 and 62 respectivelyshow the valgus and varus values at maximum allowable soft tissuetension, as a result of the lateral movements depicted in FIG. 17A, asmeasured by the force measurement 52. The graph of FIG. 17B is the ROManalysis, done preoperatively or post-operatively.

A similar graph may be produced by the implant assessment 54, toillustrate the impact of given implants at a given location on thebones. However, as shown in FIGS. 18A and 19A, the model of the implantI may be rotated by an operator, with angle values being instantlyupdated. As a result of such virtual adjustments, the varus/valgusbalanced line 60 may shift to reduce the valgus as in 60A (FIG. 18B) orto reduce the varus as in 60B (FIG. 19B). An operator or a processorperforming the implant assessment 54 may therefore perform suchadjustment in order to bring the balanced line 60 closer to a neutralvarus/valgus through as much of the leg extension as possible.

Referring now to FIGS. 20, 21, 22A-F, and 23A-23B, a surgical workflowthat may be operated with the CAS system 10 is described, with referenceto GUIs 100-130. The expression GUI is used in the plural to indicate avariation of GUI pages in the surgical workflow. The surgical workflowmay be the output D produced by the processor of the CAS controller 50.

Referring to FIG. 20, GUI 100 is provided to guide an operator duringcalibration (also known as registration) of the bones for subsequenttracking. The calibration is performed so as to position the limbs in auniversal X, Y, Z coordinate system. The origin and orientation of theX, Y, Z coordinate system may be arbitrary, or may be fixed to the ORtable or any other structural point, or may be even fixed to a bone ofthe patient. In the example of FIGS. 20, 21, 22A-F, and 23A-23B fortotal knee replacement, the femur and the tibia of the patient are to betracked, whereby their position or orientation (i.e., their location) inthe coordinate system must be set. The GUI may provide a visual displayof the femur, with animation to suggest movements to be performed duringthe calibration. According to an embodiment, the femoral head center isdetermined using the processor to perform a ROM analysis 53 to record aplurality of femur positions and orientations, essentially forming asphere whose center is that of the femoral head. In an embodiment, thepoints are acquired when the femur is moved in a conical pattern, forexample manually. The GUI 100 may guide the operator in indicating thenumber of positions required, and in confirming that a suitable numberof points have been acquired. The GUI 100 may then request that aplurality of known landmarks be digitized with a tracked digitizer tool(e.g., a tracked pointer, wand, or the registration tool described withrespect to FIG. 28 below), such as the mechanical axis entry point, themedial epicondyle, the lateral epicondyle, the anterior and posteriorWhiteside's lines, the anterior cortex, or the medial and lateralcondyles. The acquisition of these points may enable the generation of acloud of points or surface model that may be matched or merged with thebone model B of the femur (FIG. 1), via the ROM analysis 53. Hence, atthe outset of the steps directed by GUI 100, the femur is tracked in thecoordinate system.

Referring to FIG. 21, GUI 110 is also provided to guide an operatorduring calibration (also known as a registration), but for a secondbone, i.e., the tibia, to locate the tibia in the X, Y, Z coordinatesystem. The GUI 110 may request that a plurality of known landmarks bedigitized with a tracked digitizer tool, such as the malleoli, thetibial mechanical axis entry point, points on the medial plateau and onthe lateral plateau, or other points such as the medial ⅓ of tuberosity.Although not shown, the GUI 110 could suggest that a pivoting motion ofthe tibia relative to the femur be done to record the movement via thetracking device 70 and use the information to determine a mechanicalaxis of the tibia. As observed from FIG. 21, the GUI 110 may provideassistance by visual showing the regions of the tibia and fibula inwhich points are to be digitized. The acquisition of these points mayenable the generation of a cloud of points or surface model that may bematched or merged with a bone model B of the tibia (FIG. 1), via the ROManalysis 53. Hence, at the outset of the steps directed by GUI 110, thefemur and tibia are tracked in the coordinate system.

Referring to FIGS. 22A-22F, GUI 120 is used to guide the gathering ofrange-of-motion data of the tracked limbs, tracked in the coordinatesystem pursuant to the steps performed using GUIs 100 and 110. In anembodiment, the GUI 120 guides a human operator, such as a surgeon ormedical professional, in determining the limits of the range of motionand of joint laxity, based on force felt by the operator, as analternative to using the force feedback capability of the robotizedversion of the system 10. According to FIG. 22A, a lateral leg display121 may be provided to visually illustrate the limits of flexion andextension, with related angle. The operator manually displaces the tibiarelative to the femur between maximum (flexion) and minimum (extension)angles, and the tracking of the tibia and femur by the tracking device10 allows the processor to record these angles for use in the ROManalysis 53. The operator may assist in determining the maximum andminimum angle, by judging when to stop the extension and flexion basedon the resistance felt. The leg display 121 may present the measureddata in different forms, using for instance a movement arch 121A tovisually show the range of movement. A ROM bar 121B may also beprovided, showing the numerical values of angle, including a medianangle. When the extension angle value is outside of standards, the ROManalysis 53 may identify potential flexion contracture to influence theresection planning to remedy this issue. When the overall range ofmotion is below acceptable standards, the ROM analysis 53 may identifythis condition to influence resection planning and implant selection.

According to FIG. 22B, a frontal leg display 122 may also be provided inGUI 120 to visually illustrate the varus/valgus angles at extension andflexion. In a first step, the operator manually extends the leg, to thenpivot the tibia relative to the femur to maximum varus and valgusangles, and the tracking of the tibia and femur by the tracking device70 allows the ROM analysis 53 to use these angles. The maximumvarus/valgus angles may be determined by the operator's judgement as towhen to stop the extension and flexion based on the resistance felt. Thefrontal leg display 122 may provide the data in different forms, usingalso for example a movement arch 122A to visually show the range ofmovement, and an extension varus/valgus bar 122B, showing the numericalvalues of varus and valgus.

Then, according to FIG. 22C and using the same or another fontal legdisplay 122 and movement arch 122A, the operator manually flexes theleg, to then pivot the tibia relative to the femur to maximum varus andvalgus angles, and the tracking of the tibia and femur allows the ROManalysis 53 to use these angles. A flexion varus/valgus bar 122C maythen show the numerical values of varus and valgus. These values arerecorded for subsequent use by the processor in performing the softtissue balancing 56. Moreover, these values may indicate a loose ortight knee condition, laterally or medially, whether it be correctableby implant positioning or not. In the latter case, the system 10 maysuggest ligament releasing to remedy the condition. The soft tissuebalancing 56 may identify such a condition by being programmed withacceptable varus/valgus angle ranges. The varus/valgus angles obtainedmay be representative of the laxity of the medial and of the lateralcollateral ligaments, as these ligaments delimit knee laxity. When theposterior and the anterior cruciate ligaments have not been resected(e.g., in a cruciate retaining surgery), these ligaments may also affectlaxity. The knee articular capsule and the patellar tendon may alsoaffect joint laxity.

Referring to FIG. 22D, an enlarged joint display 123 may also beprovided to visually illustrate the anterior and posterior drawerdistances at flexion. To gather the information, with the leg flexed,the operator manually pushes and pulls the tibia relative to the femurto maximum posterior and anterior positions, and the tracking of thetibia and femur by the tracking device 70 allows the ROM analysis 53 touse the drawing positions, relative to a neutral position at which thetibia is natively positioned relative to the femur by soft tissuetension. Again, the maximum distances may be determined by theoperator's judgement as to when to stop the pushing and pulling based onthe resistance felt. The joint display 123 may have different forms,using a distance scale 123A to visually show the range of movement, anda distance bar 123B, showing the numerical values of varus and valgus.These values are recorded for subsequent use during the soft tissuebalancing 56. Joint displays 123A and 123B may also indicate a targetlaxity (for comparison) which is programmed to reflect the ideal laxity.The ideal laxity may be based on a surgeon-defined preference orsuggested value from literature.

Therefore, at the outset of the surgical workflow steps guided by GUI120, the system 10 has recorded joint laxity data. The recordedinformation may be based on force feedback felt by the surgeonmanipulating the tibia relative to the femur, or may be the result ofmanipulations by robotized components using sensors A and output by theforce measurement 52 when the robotized components are programmed tolimit force values. The recorded range of motion and joint laxityinformation may include maximum flexion angle, maximum extension angle,range of motion, varus and valgus angle values at extension, at flexion,or at any desired angle, anterior drawer distance, posterior drawerdistance. The recorded information may be as a function of 3D bonemodels B of the tibia and femur, or of other bones in different surgicalprocedures. The order of information gathering using the GUI 120 may bechanged from the order described above.

FIGS. 22E-22F illustrate graphical user interfaces (GUIs) 2200A and2200B, which may be used for displaying flexion/extension angle, gaps,varus and valgus angles of a knee in accordance with some embodiments.The GUIs 2200A and 2200B include a video component 2208 to displayreal-time range of motion. The GUIs 2200A and 2200B include one or moregraphical information components. For example, GUI 2200A shows thevarus/valgus angle 2206 at 6 degrees varus in the medial direction at anflexion angle 2204 of 50 degrees (from full extension at 0 degrees). GUI2200B shows the varus/valgus angle 2206 at 5 degrees varus in the medialdirection at an flexion angle 2204 of 59 degrees (from full extension at0 degrees). Additional information is shown at graphical informationcomponent 2202 in the GUIs 2200A and 2200B. The graphical informationcomponent 2202 includes gap information, varus/valgus angle information,range of motion information, and extension/flexion information. Therange of motion information may be used to create a preoperative plan.

In an example, one or more of the GUIs 2200A or 2200B may provide aremote video or allow for a remote audio connection, such as with aremote surgeon. The remote video or remote audio may be a real-timeconnection to allow the remote surgeon to discuss a procedure or providetraining with a local surgeon or to monitor the local surgeon. A GUIused by the remote surgeon may provide the remote surgeon with a videodisplay of a surgical field operated by the local surgeon.

Referring to FIGS. 23A and 23B, GUI 130 is used for the planning of theimplant positions and orientations, taking into consideration jointlaxity and range of motion as obtained using GUI 120. The GUI 130receives output from the implant assessment 54 and from the soft tissuebalancing 56. The GUI 130 may have a joint display 131 showing bonemodels B with implant models C. The joint display 131 may include a viewof the knee in extension (FIG. 23A) and a view of the knee in flexion(FIG. 23B). According to an embodiment, the user of GUI 130 may togglebetween flexion and extension views, and may also toggle between frontal(FIGS. 23A and 23B), sagittal or axial planes of view, on preference.The initial or proposed location of the implant models C relative to thebone models B may be determined by the implant assessment 54 using thejoint laxity data output by the soft tissue balancing 56. The currentlocation may be quantified using different markers, such as thosedescribed below. Joint-line variation plane 131A may display thepre-operative joint line versus the proposed joint line or the currentjoint line (i.e., actual location, as modified) when an operator variesthe location of either one of the implant models C. Lateral laxity scale132A and medial laxity scale 132B may provide a visual indication of theacceptable lateral and medial soft tissue tension. In FIGS. 23A and 23B,the acceptable range is indicated by upper and lower limits, along witha pointer indicating the tension at the current implant locations. Thescales 132A and 132B may also provide gap distances, current femur andtibia varus/valgus angles, and an anterior gap for patellofemoral jointstuffing as additional data representative of joint laxity. The gapdistances may be the sum of planned resection and ligament laxitycompared to implant thickness. According to an embodiment, the laxityscales 132A and 132B dynamically reflect modifications to the plannedimplant location. The adjustments on the laxity scales 132A and 132B maybe reflected by the graphs shown in FIGS. 18B and 19B, as a function ofa rotation of the implant. A femoral component window 133 may enable thechange of femoral implant size. The user may have the possibility ofchanging implant sizes, in which case the displayed femoral implantmodel and related information on the joint display 131 may be updated(131A, 132A, 132B, etc.). A spacer component window 134 may enable theselection of the spacer thickness or the type of spacer. Changes to thespacer component may result in a dynamic update of the joint display 131and of related data (131A, 132A, 132B, etc.). A tibial component window135 may enable the change of tibial implant size, with the user giventhe option of changing implant sizes, in which case the displayed tibialimplant model and related information on the joint display 131 may bedynamically updated (131A, 132A, 132B, etc.). A location control panel136 is provided for the user to modify the location of the femoralcomponent relative to the femur, in translation or location. As thelocation is modified using the location control panel 136, the jointdisplay 131 may be updated and applicable data is also adjusted, such131A, 132A, 132B, etc. Alternatively or additionally, the implants inthe joint display 131 may be widgets that may be moved around relativeto the bone models B, with the consequential dynamic adjustment ofapplicable data (e.g., 131A, 132A, 132B). The widget feature may beavailable in all views. It has the same function whether it is overlaidon the knee or on the left panel of GUI 130: it allows the user toposition/orient the implant with respect to the bone. The effect ofchanging position or orientation of the implant will be dynamicallyreflected in the laxity scales. The laxity scales will be different inflexion and extension. The laxity scales could be provided throughoutall angles of flexion.

Accordingly, the processor may perform the implant assessment 54 or thesoft tissue balancing 56, and may propose implant components andlocations for the implant components via the GUI 130. The GUI 130 givesthe possibility to an operator to modify the implant components or theirlocations, by dynamically updating in real-time quantitative datarelated to joint laxity and range of movement, to assist the operator isfinalizing the resection planning. When the implants are selected andtheir locations are set, the information of the GUI 130 is convertedinto another form of the output D, such as personal surgical instrumenttool files or data to perform resection as decided, a navigation filefor the robot arm 20 when present, or a navigation file for trackedtools. The GUI 130 may also be used post-resection, to provide the jointlaxity data for the “as-resected” state. The data may be used todocument the surgical procedure. This may also allow post-resectioncorrections when deemed necessary. It may be required to return to GUI100 or 110 to recalibrate the bones to obtain more precision in theassessment.

FIG. 24 illustrates a tibial force detection system 2400 in accordancewith some embodiments. The tibial force detection system 2400 includes atibial baseplate 2402 including one or more force detection components.In an example, the tibial baseplate 2402 includes four force detectioncomponents, corresponding to four quadrants, which are labeled in FIG.24 as quadrants ‘A’, ‘B’, ‘C’, and ‘D’. The quadrants may be dividedsuch that each quadrant is moveable independently in at least one axisrelative to the other quadrants. For example, dividing line 2404illustrates a separation between quadrants B and C, such that quadrantsB and C may be compressed or decompressed relative to each other. Theforce detection components may be located within the quadrants (e.g.,within the tibial baseplate 2402 (e.g., underneath a first layer shownin FIG. 24). As a quadrant is compressed or decompressed, the forcedetection component corresponding to that quadrant may include a sensorto detect the compression force (or measure a decompression force orchange in force). In another example, the quadrants may be immovablerelative to each other, while still including corresponding forcedetection components to measure force in each quadrant independently. Inyet another example, the tibial baseplate 2402 may be divided intohalves, with each half including a corresponding force detection sensorand being moveable relative to the other half. In yet another example,further subdivisions may be made of the tibial baseplate 2402 includingcorresponding force detection components and independent movement (e.g.,six, eight, etc., radial slices of the tibial baseplate 2402). The forcedetection components may be used to obtain data regarding force impartedon the tibial baseplate 2402 intraoperatively.

In an example, the knee may be opened and a navigated tibial cut may bemade. In an example, variances in the tibial cut may be related to adepth of the cut, which may be relatively standard for most surgeonstaking reference from either the high or low tibial plateau. Once thetibial cut has been made the tibial force detection system 2400 may beplaced. The tibial force detection system 2400 may include a tibialbaseplate and a polyethylene trial combination. The tibial forcedetection system 2400 may expand medially and laterally, such as toaccommodate various sized knees. In an example, the tibial forcedetection system 2400 may have a medial or lateral tilting hemi-plateauwith the ability to rise and fall all four quadrants independently. Thedisplacement up and down and the force experienced by each quadrant maybe measured, such as electronically or hydraulically using a sensor. Inan example, the tibial force detection system 2400 may be an activedevice such that upward or downward movement may be measured as the knee(e.g., before femoral cuts are performed) is put through a range ofmotion test. In an example, measuring the movement during the range ofmotion test may be performed while tracking the patella. In an example,varus or valgus forces may be applied, such as by a robotic arm on theknee or by a surgeon through a range of motion (e.g., the entire rangeor a predetermined interval, such as 10, 30, 60, 90 degrees, or asperformed by the surgeon). The sequence may be repeated with apre-stress test to better appreciate the knee mechanics, for example,after correction for a lax medial collateral ligament (MCL) or lateralcollateral ligament (LCL). In an example, the sequence may be repeatedafter the femoral cuts have been made or after the femoral trial isseated to provide an opportunity for further improvements to the trialor to optimize soft tissue balancing.

In an example, when a knee requires soft tissue releases, the releasesmay performed in a staged and sequential fashion and a re-assessment ofthe improved kinematics may be performed, for example, after eachintervention. This process allows a quantification of knee kinematicsduring different measurement points intraoperatively. Thequantifications may be used to balance the soft tissue more accuratelythan previous techniques. The quantifications may be saved to adatabase, such as for modeling, machine learning to predict outcomes infuture cases, or the like. In an example, an indication may be providedto a surgeon regarding useful releases for a particular patient. Inanother example, an indication of femoral component sizing AP, locationAP, or rotation may be provided to improve flexion/extension gapsthroughout the range 0 to 90 degrees, which may include accounting for alocation of the patella by using the patella tracking.

In an example, a robotic arm may be used to assess bone quality. Usingthe assessed bone quality, a system may determine whether to use bonecement or to stem a patient when placing an implant, such as the tibialbaseplate 2402. In another example, the tibial baseplate 2402 may behydraulically powered. The hydraulic power may be used to cause thetibia or femur to rotate to a tension rotation angle automatically. Theangle may be recorded, such as by using sensors within the tibialbaseplate 2402. The tibial baseplate 2402 may be used to expand the gapbetween the tibia and the femur.

FIGS. 25A-25B illustrate a patella sensor 2504 of a range of motiontesting system in accordance with some embodiments. A first view 2500Aillustrates a side view of a patella 2502 with the patella sensor 2504,including relative placement of the patella 2502 with respect to a femur2506 and a tibia 2508. A second view 2500B illustrates a back view ofthe patella 2502 with the patella sensor 2504.

In an example, the patella sensor 2504 may be placed on the back of thepatella 2502, for example prior to an incision or bone cut. The patellasensor 2504 may be used to determine patella position during a range ofmotion test. For example, the patella sensor 2504 may include anaccelerometer, a magnetometer, a gyroscope, an RFID chip, an opticaltracking sensor, or other location sensor. In an example, the patellasensor 2504 may be located around the periphery of the patella 2502, forexample to detect and output the outline of the patella 2502. In anotherexample, a size of the patella 2502 may be measured (e.g., viapreoperative or intraoperative imaging or direct measurement), and aposition of the patella sensor 2504 relative to the patella 2502 may beknown, allowing a location of the entirety of the patella 2502 to beknown.

The location of the patella 2502 may be used during a surgicalprocedure, such as a knee replacement. During a knee replacementprocedure, a robotic arm may be used to perform aspects of theprocedure. The robotic arm may use the detected location of the patella2502 (from the patella sensor 2504) to perform a patella cut or to avoidthe patella while making other cuts. In an example, the patella sensor2504 may be a passive sensor. In an example, a tracking assembly may beused, such as that described in U.S. Pat. No. 8,571,637 to BiometManufacturing, LLC, which is herein incorporated by references in itsentirety.

FIGS. 26A-26B illustrate augmented reality systems for control of arobotic arm 2602 in accordance with some embodiments. FIGS. 26A-26Binclude two example embodiments. The augmented reality systems usevirtual components to control real world objects. An augmented reality(AR) device allows a user to view displayed virtual objects that appearto be projected into a real environment, which is also visible. ARdevices typically include two display lenses or screens, including onefor each eye of a user. Light is permitted to pass through the twodisplay lenses such that aspects of the real environment are visiblewhile also projecting light to make virtual elements visible to the userof the AR device.

Augmented reality is a technology for displaying virtual or “augmented”objects or visual effects overlaid on a real environment. The realenvironment may include a room or specific area (e.g., a surgicalfield), or may be more general to include the world at large. Thevirtual aspects overlaid on the real environment may be represented asanchored or in a set position relative to one or more aspects of thereal environment. For example, a virtual robotic arm 2604 of FIG. 26Amay be displayed in a set location of a surgical field, to be controlledby a surgeon using an AR device. An AR system may present virtualaspects that are fixed to a real object without regard to a perspectiveof a viewer or viewers of the AR system (e.g., the surgeon 102). Forexample, the virtual object 2604 of FIG. 26A may be configured to appearto be an offset distance away from the robotic arm 2602. In an example,virtual objects may appear to have a degree of transparency or may beopaque (i.e., blocking aspects of the real environment).

A surgeon may control the virtual robotic arm 2604 by interacting withthe virtual robotic arm 2604 (e.g., using a hand to “interact” with thevirtual robotic arm 2604 or a gesture recognized by a camera of the ARdevice). The virtual robotic arm 2604 may then be used to control therobotic arm 2602. For example, the surgeon may move the virtual roboticarm 2604 and the robotic arm 2602 may move correspondingly.

In the example shown in FIG. 26B, one or more virtual control arms(e.g., 2606 or 2608) may be used to control movement of the robotic arm2602. For example, a surgeon may move the virtual control arm 2608 tocause the robotic arm 2602 to move in a corresponding fashion. Usingmore than one virtual control arm may allow for independent degrees offreedom in controlling the robotic arm 2602. For example, a surgeon mayrotate his or her hand to virtually “twist” the virtual control arm2606, which may cause an end effector of the robotic arm 2602 to rotate,without translating the robotic arm 2602. Similarly, the virtual controlarm 2608 may be moved to cause the robotic arm 2602 to translate withoutrotating.

In an example, aspects of the robotic arm 2602 may be controlled bypressing one or more virtual buttons that may appear virtually overlaidin a real environment. For example, a button may be displayed virtuallyto cause the robotic arm 2602 to move to a first position to aid inperforming or to perform a surgical technique. Using the virtual buttonallows the surgeon to remain in place without needing to turn or averthis or her vision to a display device. This allows the surgeon tomaintain focus on the surgical field and monitor the robot, as well asreducing time for the procedure.

In an example, using virtual control elements (e.g., 2604, 2606, or2608) to control the robotic arm 2602 to perform a procedure may avoidthe use of force sensing. For example, instead of controlling therobotic arm 2602 using force sensing when a surgeon moved the roboticarm 2602, the robotic arm 2602 may respond to movements of the virtualcontrol elements. In another example, force sensing may be used inaddition to the augmented reality elements described above. For example,force sensing may be used to communicate information to a system usingthe robotic arm. For example, tapping on the robotic arm 2602 may causethe robotic arm 2602 to lock in place, confirm actions, deny actions,etc. In another example, information may be communicated using virtualbuttons as described above. Using the virtual control elements may allowthe robotic arm 2602 to be driven in an active mode throughout aprocedure, instead of having non-active modes or locations where theactive mode is disabled.

FIG. 27 illustrates a system 2700 for distracting a femur from a tibiain accordance with some embodiments. The system includes a leg holder2704 connected to a support structure 2708 via a support device 2706,the leg holder 2704 supporting a patient's knee 2702. The support device2706 may include a force applicator, such as a hydraulic device, motor,etc., to apply pressure under the femur, for example while the leg isunder extension. In another example, the support device 2706 may beconnected to a robotic arm, which may be used to apply a force.

FIG. 28 illustrates a robotic arm registration system 2800 in accordancewith some embodiments. The robotic arm registration system 2800 includesa robotic arm 2802, an end effector 2804 attached to a distal end of therobotic arm 2802, and a landmark registration identifier 2806 attachedto the end effector 2804. The landmark registration identifier 2806 maybe used to automatically identify landmarks by using the robotic arm2802 to navigate to different points of a patient's anatomy. Forexample, the robotic arm 2802 may be connected to a system that maytrack the robotic arm 2802 or the patient's anatomy. Using trackingdata, the robotic arm 2802 may navigate the patient's anatomy toautomatically find and tag points using the landmark registrationidentifier 2806. In an example, the landmark registration identifier2806 may include a claw tool to register landmarks at angles that mayotherwise be difficult to reach with a straight tool.

FIG. 29 illustrates a flow chart showing a technique 2900 for using arobotic arm to perform soft tissue balancing in accordance with someembodiments. The technique 2900 includes an operation 2902 to apply aforce to a bone of a patient joint using a robotic arm. The technique2900 includes an operation 2904 to measure the force to capture dataindicative of soft tissue tension in the patient joint. The technique2900 may include an operation to track, using a processor, movement ofthe robotic arm, which may include capturing tracking data. Thetechnique 2900 includes an operation 2906 to determine soft tissuetension at the patient joint based on the force data. The soft tissuetension may be determined using the tracking data. The technique 2900may include an operation to output the soft tissue tension. Thetechnique 2900 may include receiving patella location information from asensor affixed to a back side of the patella. The technique 2900 mayinclude outputting the patella location information during a range ofmotion test. The technique 2900 may include controlling the robotic armusing a virtual component displayed using an augmented reality device.In an example, tracking aspects of the patient's anatomy may beperformed using a pneumatic cuff sensor on the patient's anatomy. In anexample, the bone may be a tibia or a femur.

FIG. 30 illustrates a flow chart showing a technique 3000 for using arobotic arm to perform a soft tissue pull test in accordance with someembodiments. In an example, the technique 3000 includes an operation3002 to resect a distal femur and an operation 3004 to resect a proximaltibia. In an example, the technique 3000 includes an operation 3006 toperform a soft tissue balancing test, such as a ligament test while ajoint connecting the femur to the tibia is in extension. Operation 3006may be performed with spacer component or a shim device to put the jointunder tension. After operation 3006, the technique 3000 may includeperforming a release, such as of a ligament or a tendon. The technique3000 includes an operation 3008 to insert a soft tissue balancingcomponent, such as a spike, condyle pivot, j-shaped adapter, or thelike. Once inserted, the soft tissue balancing component may be used toperform a pull test, such as when the joint is in flexion to determine arotation required to balance ligaments in the joint.

The technique 3000 includes an operation 3010 to use the determinedrotation to calculate pin placement for a cut guide (e.g., a 4-in-1 cutguide) to obtain a desired or predetermined femoral component rotation.Operation 3010 may be performed by a processor, such as using surgicalprocedure planning software to provide instructions to the processor.The technique 3000 includes an operation 3012 to output pin placementlocations or to place pins for the cut guide. The technique 3000includes an operation 3014 to perform cuts using the placed cut guide.In an example, a tibial cut may be performed, optionally after operation3014 or before operation 3002. In an example, any one or more ofoperations 3002, 3004, 3006, 3008, 3012, 3014, or the tibial cut may beperformed using a robotic arm. In another example, the technique 3000may include an operation to output a pin placement using the rotationangle for updating a preoperative plan intraoperatively. The output pinplacement be used instead of preoperative pin placement locations, or anaverage or weighted average may be used.

In an example, the technique 3000 may include an optional operation 3016to apply a force to a bone, such as the femur or the tibia, to perform asoft tissue balancing test, using an end effector of a robotic arm,which may apply a force to the soft tissue balancing component. In anexample, the technique 3000 may include an optional operation 3016 tooutput information about soft tissue balance. In another example, thetechnique 3000 may include applying a force to the femur or the tibiausing the soft tissue balancing component without the use of a roboticarm.

FIG. 31 illustrates a flow chart showing a technique 3100 for performingrobot-aided surgery using tracking in accordance with some embodiments.The technique 3100 includes an operation 3102 to track movement of abone using a tracking system, such as an optical tracking system. Thetracking system may include a first tracker affixed to a bone of apatient. In an example, the tracking system includes a second trackeraffixed to a second bone of the patient. In an example, the trackingsystem includes a third tracker affixed to a robotic arm. The technique3100 may include receiving tracking information from the tracking systemincluding position or orientation information for the third trackeraffixed to a portion of the robotic arm. The tracking position ororientation of the robotic arm may be used to track an end effectorlocated at a distal end of the robotic arm, at least in part, using theposition and orientation information from the second tracker.

The technique 3100 includes an operation 3104 to monitor a position andorientation of an end effector coupled to the end of a robotic arm, forexample using a robotic controller. The technique 3100 includes anoperation 3106 to move the robotic arm to a soft tissue balancing testposition and orientation relative to the bone. The technique 3100includes an optional operation 3108 to control the robotic arm to retainthe position and orientation relative to the bone when the bone moves,for example using the robotic controller. The optional operation 3108may include receiving an indication of movement of the bone from thetracking system. The technique 3100 includes an operation 3110 to applya force to the bone using an end effector of the robotic arm. Thetechnique 3100 includes an optional operation 3112 to track a positionand orientation of the end effector when moved by the roboticcontroller.

The technique 3100 includes an operation 3114 to determine soft tissuebalance using the position and orientation of the end effector orinformation from the tracking system, such as a position of the firsttracker affixed to the bone. In an example, determining the soft tissuebalance may include using force information from a force sensor coupledbetween the end effector and the robotic arm. The technique 3100 mayinclude an operation to identify manual movement of the end effectorusing a force sensor and allowing the manual movement of the endeffector relative to the bone. In an example, the end effector may becoupled to a distal end of a bone spike after the bone spike is coupledto the bone. The technique 3100 may include an operation to output thesoft tissue balance, such as for display on a user interface.

The technique 3100 may include an operation to release the force on thebone when the soft tissue balancing test indicates that soft tissueconnected to the bone is in balance, when a threshold force is reached,when a threshold tension is reached, when a predetermined distance(e.g., a distance equal to a tibial implant thickness), or the like.Releasing the force on the bone may include returning the force to zero,such as by increments. For example, the soft tissue balancing testindicates that the soft tissue connected to the bone is in balance basedon detecting the bone in a pre-determined orientation during the test.In another example, the soft tissue balancing test indicates that softtissue connected to the bone is in balance when sufficient data iscollected to determine a balance in the soft tissue, and wherein thebalance is an indication of the difference in tension between a medialside and a lateral side of the joint. The balance may indicate an anglefor a resection cut to be made in a joint replacement procedure. Thetechnique 3100 may include an operation to perform a release of aportion of soft tissue connected to the bone based on the soft tissuebalance. The technique 3100 may include an operation to output, forexample for display on a user interface, an indication of soft tissuebalance or an angle of rotation of the bone relative to a second bone.

The technique 3100 may include an operation to calculate a targetfemoral implant rotation using a determined rotation of the femur duringa soft tissue balancing test. For example, the determined rotation usedmay be when the gap balance is equal to a predetermined gap distance.The target femoral implant may be the inverse or opposite of thedetermined rotation. In an example, the technique 3100 may include anoperation to store the target femoral implant rotation, such as inmemory or a database, for use by planning software.

FIG. 32 illustrates a flow chart showing a technique 3200 for performingrobot-aided surgery using a force sensor in accordance with someembodiments. The technique 3200 includes an operation 3202 to secure abone spike in a distal end of a first bone in a joint of a patient. Thetechnique 3200 includes an operation 3204 to measure resistance in softtissues connected to the first bone using a force sensor of a softtissue balancing device coupled to a distal end of the bone spike via aspike socket.

The technique 3200 includes an operation 3206 to manipulate the softtissue balancing device during the soft tissue balancing test using arobotic arm. The operation 3206 may include applying tension to thejoint using the robotic arm through the soft tissue balancing deviceduring the soft tissue balancing test. The technique 3200 includes anoperation 3208 to output an indication of tension in the soft tissueduring a soft tissue balancing test. In an example, the first bone is afemur, and the soft tissue includes ligaments connecting the femur to atibia of the patient joint. The technique 3200 may include using therobotic arm is to manipulate the soft tissue balancing device with thefemur and the tibia in flexion or extension.

The technique 3200 may include an operation to output, from the roboticarm, a resection angle for an at least partial joint replacement to acomputing device to calculate soft tissue balance in the joint. Thecomputing device may be used to calculate a pin placement location for acut guide based on the resection angle. In an example, a pin placementtrial or pins may be positioned or placed, for example using the roboticarm, at a location on the first bone according to the pin placementlocation. The technique 3200 may include an operation to output, from aforce sensor, force data indicative of soft tissue tension in thepatient joint when the force is applied to the first bone by the softtissue balancing component. In an example, soft tissue tension may bedetermined at the patient joint based on the force data.

The technique 3200 may include an operation to move the robotic arm to asoft tissue balancing test position and orientation relative to thefirst bone. In an example, the robotic arm may be controlled to retainthe position and orientation relative to the first bone when the bonemoves. The operation may include applying a force to the first boneusing the soft tissue balancing component. The operation may includetracking movement of the first bone using an optical tracking systemincluding a first optical tracker affixed to the first bone of thepatient and a second optical tracker affixed to the robotic arm. Theoperation may include determining the tension in the soft tissue duringa soft tissue balancing test using the tracked movement of the firstbone. The operation may include tracking a position and orientation ofthe soft tissue balancing component when moved, and determining softtissue tension using the position and orientation of the end effectorand information from the optical tracking system including a position ofthe second optical tracker affixed to the robotic arm and a position ofthe first optical tracker affixed to the first bone. In an example, theoperation may include determining a tension in medial soft tissue and atension in lateral soft tissue using a force vector of the soft tissuebalancing component on the first bone provided by the force sensor and arelative bone orientation of the first bone to a second bone provided bythe optical tracking system.

FIGS. 33A-33D illustrate example user interfaces 3300A-3300D for jointreplacement surgical planning in accordance with some embodiments. Userinterface 3300A of FIG. 33A includes a cut checklist 3302 to illustratecuts that have been performed or that are not yet completed. Userinterface 3300A includes an interactive user guide 3304 showing a softtissue balancing test overview. The user guide 3304 shows a targetimplant rotation with respect to a femur to give a balanced flexion gap.The user guide 3304 shows four steps of the soft tissue balancing test,from an initial state, to pulling on the femur, to showing a gapimbalance, to finally showing a rotation to align the soft tissue.

User interface 3300B of FIG. 33B includes a second user guide 3306including instructions on how to insert a spike 3308 to connect a softtissue balancing component 3310 to a femur 3312. The spike 3308 holdsthe soft tissue balancing component 3310 in place, but may allow thefemur 3312 to rotate. The soft tissue balancing test may be initiated,for example, by pressing a foot pedal, which is indicated in the seconduser guide 3306. In an example, the soft tissue balancing test may beperformed with a patella or soft tissue in place by using a j-shaped orhook-shaped soft tissue balancing component 3310. When the soft tissuebalancing test is initiated, a robotic arm may pull the soft tissuebalancing component 3310, such as by using an end effector connectingthe robotic arm to the soft tissue balancing component 3310 to apply aforce on the spike 3308, which may in turn cause a force on the femur3312, for example to move the femur 3312 away from a tibia.

User interface 3300C of FIG. 33C includes a third user guide 3314 whichshows an illustration of a patient joint including a current imbalanceat a particular gap distance, while superimposing a proposed balance(e.g., based on completed releases, cuts, and implants added to thejoint). The third user guide 3314 includes information related to acurrent rotation or a target femoral implant rotation (e.g., therotation information may change over time or during a procedure, such asfrom a current rotation to a target rotation, or may show both, or adifference). The distance pulled (e.g., over time or at a current time)is also illustrated in the third user guide 3314. The third user guide3314 may include user-selectable options to apply a target femoralimplant rotation to a 3D plan or to not apply the target femoral implantrotation to the 3D plan. The 3D plan may include preoperative orintraoperative plans. Adding the target femoral implant rotation to the3D plan may include adding it to the 3D plan as is, or with changes(e.g., surgeon adjustments).

The user guide 3314 may include a force bar 3313 or a distance bar 3315.The force bar 3313 may be used to display a current pulling force (e.g.,of a robotic arm on the femur). In an example, the robotic arm may bestopped automatically by a robotic controller when the force reaches amaximum force, which may be displayed on the force bar 3313. In anexample, a surgeon may control the robotic arm by adjusting the forcebar 3313. The distance bar 3315 may move simultaneously with the forcebar 3313 in an example. The distance bar 3315 shows a distance pulled,such as a distance from the femur to the tibia (whether the femur or thetibia is pulled). In an example, the distance bar 3315 may be controlledby a surgeon to move the robotic arm similar. In an example, thedistance bar 3315 may include a maximum distance pulled, which when thefemur and the tibia are separated by the maximum distance, the roboticarm may be stopped.

User interface 3300D of FIG. 33D includes a fourth user guide 3316,which shows rotation of a femur in a knee joint in various views. Thefemur may be viewed in flexion with respect to a tibia or in extension.When used intraoperatively, as the joint is placed in these differentorientations, the user guide 3316 may be automatically updated (e.g.,using trackers).

One or more of user guides 3304, 3306, 3314, or 3316 may includeinformation on ligament balance. For example, a soft tissue balancingtest may be performed, and force information, tension information, orother sensor data may be sent to the one or more of user guides 3304,3306, 3314, or 3316 to display soft tissue balance, such as a rotationangle to balance the ligaments. In another example, the one or more ofuser guides 3304, 3306, 3314, or 3316 may display a measured resectiontechnique, for example by providing feedback on actual measured anglesor detected forces after or before resection, in addition to therotation angle at which there is balance.

In an example, medial and lateral borders of a tibial tubercle may beidentified and used to determine a medial third landmark location. Theone or more of user guides 3304, 3306, 3314, or 3316 may display themedial and lateral borders or the medial third landmark location. Forexample, a robotic arm may be used to identify a most medial boundary ofa tibial tuberosity. The robotic arm may be used to identify a mostlateral boundary of the tibia tuberosity. A system may use theseidentified boundaries to accurately display and locate a location knownas a medial third location on the tibial tuberosity. Identifying thislocation may not be reproducibly performed with conventionalinstrumentation, such as with sub-millimeter metric precision. Thislocation may be used to assist in a rotational placement of a tibialbase plate for a knee arthroplasty as a reference point.

VARIOUS NOTES & EXAMPLES

Each of these non-limiting examples may stand on its own, or may becombined in various permutations or combinations with one or more of theother examples.

Example 1 is a robot-aided surgical system comprising: a tracking systemincluding a first tracker affixed to a bone of a patient, the trackingsystem configured to track movement of the bone; a robotic controllerto; monitor a position and orientation of an end effector coupled to anend of a robotic arm; apply a force to the bone using the end effector;determine soft tissue balance using information from the tracking systemincluding a position of the first tracker affixed to the bone; andoutput the soft tissue balance.

In Example 2, the subject matter of Example 1 optionally includes a softtissue balancing component coupled to the end effector and configured totransfer force from the end effector to the bone.

In Example 3, the subject matter of Example 2 optionally includeswherein the soft tissue balancing component comprises at least one of aspike, a condyle pivot, a jig, or an adaptor, wherein the adaptor isshaped to avoid a patella or soft tissue of a knee joint of the patient.

In Example 4, the subject matter of Example 3 optionally includeswherein the soft tissue balancing component comprises the condyle pivot,and wherein the condyle pivot comprises a plurality of platform armseach capable of applying an individually determined force to the bone.

In Example 5, the subject matter of any one or more of Examples 3-4optionally include wherein the soft tissue balancing component comprisesthe jig, and wherein the jig includes at least one of a spacer block ora flat attachment.

In Example 6, the subject matter of any one or more of Examples 1-5optionally include a force sensor coupled to the robotic arm, andwherein to determine the soft tissue balance, the robotic controller isto use force information from the force sensor.

In Example 7, the subject matter of Example 6 optionally includeswherein the robotic controller is to determine the force informationwhen a pull test performed by the robotic arm reaches a predeterminedgap distance from the bone to a second bone, the force informationindicative of an equal force between two ligaments connecting the boneto the second bone.

In Example 8, the subject matter of any one or more of Examples 1-7optionally include wherein to output the soft tissue balance, therobotic controller is to output an indication of the degree of rotationof the bone.

In Example 9, the subject matter of Example 8 optionally includeswherein the robotic controller is to determine a location to place a cutguide for resecting the bone using the robotic arm based at least inpart the indication of the degree of rotation.

In Example 10, the subject matter of any one or more of Examples 1-9optionally include wherein the determined soft tissue balance indicatesa difference in tension between a medial side and a lateral side of aknee joint of the patient.

In Example 11, the subject matter of any one or more of Examples 1-10optionally include wherein to output the soft tissue balance, therobotic controller is to output an amount of force applied by the endeffector on the bone when the bone reaches a predetermined gap thicknessin relation to a second bone.

In Example 12, the subject matter of any one or more of Examples 1-11optionally include a cutting device to perform a release of a portion ofsoft tissue connected to the bone based on the soft tissue balance.

In Example 13, the subject matter of any one or more of Examples 1-12optionally include a display device to display an indication of theoutput soft tissue balance or an angle of rotation of the bone relativeto a second bone.

In Example 14, the subject matter of any one or more of Examples 1-13optionally include wherein the robot controller is further to determinealterations required on the bone to receive at least one implant in agiven location, using a model of the at least one implant and the softtissue balance.

Example 15 is a robot-aided surgical system comprising: a trackingsystem including a first tracker affixed to a bone of a patient, thetracking system configured to track movement of the bone; a roboticcontroller to: monitor a position and orientation of an end effectorcoupled to an end of a robotic arm; apply a force to the bone using asoft tissue balancing component coupled to the end effector, the softtissue balancing component configured to transfer force from the endeffector to the bone; and determine soft tissue balance usinginformation from the tracking system including a position of the firsttracker affixed to the bone and force information from a force sensorcoupled to the robotic arm; and a display device to display anindication of the soft tissue balance including a tension of at leastone ligament connecting the bone to a second bone or an angle ofrotation of the bone relative to the second bone.

In Example 16, the subject matter of Example 15 optionally includeswherein the indication of the soft tissue balance includes an indicationof a difference in tension between a medial ligament and a lateralligament of a knee joint of the patient.

In Example 17, the subject matter of any one or more of Examples 15-16optionally include a cut guide coupled to the robotic arm to guide aresection cut in a joint replacement procedure based on the angle ofrotation of the bone relative to the second bone.

In Example 18, the subject matter of any one or more of Examples 15-17optionally include a cutting device coupled to the robotic arm toperform a release of a portion of soft tissue connected to the bonebased on the soft tissue balance.

In Example 19, the subject matter of any one or more of Examples 15-18optionally include a cut guide coupled to the robotic arm to guide aresection on a tibia of the patient before determining the soft tissuebalance.

In Example 20, the subject matter of Example 19 optionally includeswherein the robotic controller is further to determine a pin placementlocation for a cut guide based at least in part on the angle of rotationof the bone relative to the second bone.

Example 21 is a robot-aided knee arthroplasty system comprising: a legholder to affix anatomy of a patient during an arthroplasty procedure;an end effector of a robotic arm to couple to a femur of the knee jointwith a soft tissue balancing component that permits the femur to freelyrotate while coupled to the end effector; a robotic controller to: causethe robotic arm to apply a pulling force to the femur to increase a gapdistance between the femur and a tibia of the knee joint; measure thegap distance between the femur and the tibia and a rotation of thefemur; and store, when the gap balance is equal to a predetermined gapdistance, the rotation of the femur as a target femoral implantrotation; and a surgical planning system to plan a position andorientation of a resection such that inserting a femoral implant on thefemur causes the femur to achieve the target femoral implant rotation.

In Example 22, the subject matter of Example 21 optionally includes acut guide coupled to the robotic arm to guide a cutting device toperform the resection.

In Example 23, the subject matter of Example 22 optionally includeswherein the robotic controller is to: determine a pin hole location onthe bone based at least in part on the indication of the degree ofrotation, the pin hole location determined such that a pin inserted intothe pin hole location aligns the cut guide to the bone; cause therobotic arm to place a pin guide component, coupled to the end effectorof the robotic arm, on the bone such that a drill hole of the pin guidecomponent aligns with the pin hole location.

In Example 24, the subject matter of any one or more of Examples 21-23optionally include a tracking system to track trackers affixed to thefemur and the tibia and to output tracking information, and wherein tomeasure the gap distance between the femur and tibia and the rotation ofthe femur, the robotic controller is to use the tracking information.

In Example 25, the subject matter of any one or more of Examples 21-24optionally include wherein the robotic controller is further to causethe robotic arm to apply a pushing force to the tibia and calculate atension in a lateral collateral ligament and a medial collateralligament of the knee joint as the pushing force is applied to the tibiawith the robotic arm, and further comprising a display device to displayan indication of the tension in the lateral collateral ligament and themedial collateral ligament.

Example 26 is at least one machine-readable medium includinginstructions for performing robot-aided surgery, which when executed bya processor, cause the processor to: cause a robotic arm to apply apulling force to a femur, using a soft tissue balancing componentcoupled to the femur such that the femur freely rotates, to increase agap distance between the femur and a tibia of the knee joint; measurethe gap distance between the femur and a tibia and a rotation of thefemur; and calculate a target femoral implant rotation using therotation of the femur, when the gap balance is equal to a predeterminedgap distance; store the target femoral implant rotation; and plan, usinga surgical planning system, a position and orientation of a resectionsuch that inserting a femoral implant on the femur causes the femur toachieve the target femoral implant rotation.

In Example 27, the subject matter of Example 26 optionally includesinstructions to: track trackers affixed to the femur and the tibia;output tracking information; and use the tracking information to measurethe gap distance between the femur and tibia and the rotation of thefemur.

In Example 28, the subject matter of any one or more of Examples 26-27optionally include instructions to: cause the robotic arm to apply apushing force to the tibia; calculate a tension in lateral and medialcompartments (e.g., a lateral collateral ligament and a medialcollateral ligament) of the knee joint as the pushing force is appliedto the tibia with the robotic arm; and output an indication of thetension in the lateral and medial compartments.

In Example 29, the subject matter of any one or more of Examples 26-28optionally include instructions to determine a pin placement locationfor a cut guide based at least in part on the rotation of the femur.

In Example 30, the subject matter of Example 29 optionally includesinstructions to cause the robotic arm to position a pin placement trialfor placing a pin at a location on the bone according to the pinplacement location.

Example 31 is a robot-aided surgical system comprising: a bone spikeadapted to be secured in a distal end of a first bone in a joint of apatient; a soft tissue balancing device comprising a force sensor and aspike socket couplable to a distal end of the bone spike, the forcesensor adapted to measure resistance in soft tissues connected to thefirst bone; a robotic arm to manipulate the soft tissue balancing deviceduring the soft tissue balancing test; and an output device to output anindication of tension in the soft tissue during a soft tissue balancingtest.

In Example 32, the subject matter of Example 31 optionally includeswherein the soft tissue balancing device is an end effector on therobotic arm or a j-shaped arm coupleable to the bone spike.

In Example 33, the subject matter of any one or more of Examples 31-32optionally include wherein the robotic arm applies tension to the jointthrough the soft tissue balancing device during the soft tissuebalancing test.

In Example 34, the subject matter of any one or more of Examples 31-33optionally include wherein the robotic arm and soft tissue balancingdevice provide output to a computing device to calculate soft tissuebalance in the joint.

In Example 35, the subject matter of Example 34 optionally includeswherein the soft tissue balance is output in a medial tension and alateral tension.

In Example 36, the subject matter of any one or more of Examples 34-35optionally include wherein the soft tissue balance is output as aresection angle for an at least partial joint replacement.

In Example 37, the subject matter of Example 36 optionally includeswherein the resection angle is selected to balance the soft tissue afterat least a portion of the joint is replaced with a prosthesis.

In Example 38, the subject matter of any one or more of Examples 36-37optionally include wherein the computing device is to calculate a pinplacement location for a cut guide based on the resection angle.

In Example 39, the subject matter of Example 38 optionally includeswherein the robotic arm is further to position a pin placement trial forplacing a pin at a location on the first bone according to the pinplacement location.

In Example 40, the subject matter of any one or more of Examples 31-39optionally include a retention device to restrain a second bone of thejoint of the patient during the soft tissue balancing test.

In Example 41, the subject matter of any one or more of Examples 31-40optionally include a force sensor to output force data indicative ofsoft tissue tension in the patient joint when the force is applied tothe first bone by the soft tissue balancing component.

In Example 42, the subject matter of Example 41 optionally includes aprocessor to determine soft tissue tension at the patient joint based onthe force data.

In Example 43, the subject matter of any one or more of Examples 31-42optionally include a robotic controller to: move the robotic arm to asoft tissue balancing test position and orientation relative to thefirst bone; control the robotic arm to retain the position andorientation relative to the first bone when the bone moves; and apply aforce to the first bone using the soft tissue balancing component.

In Example 44, the subject matter of Example 43 optionally includes anoptical tracking system including a first optical tracker affixed to thefirst bone of the patient and a second optical tracker affixed to therobotic arm, the optical tracking system to track movement of the firstbone, and further comprising a processor to determine the tension in thesoft tissue during a soft tissue balancing test using the trackedmovement of the first bone.

In Example 45, the subject matter of Example 44 optionally includeswherein the processor is further to: track a position and orientation ofthe soft tissue balancing component when moved by the roboticcontroller; and determine soft tissue tension using the position andorientation of the end effector and information from the opticaltracking system including a position of the second optical trackeraffixed to the robotic arm and a position of the first optical trackeraffixed to the first bone.

In Example 46, the subject matter of Example 45 optionally includeswherein the processor is to use a force vector of the soft tissuebalancing component on the first bone provided by the force sensor and arelative bone orientation of the first bone to a second bone provided bythe optical tracking system to determine a tension in medial soft tissueand a tension in lateral soft tissue.

Example 47 is a method for performing robot-aided surgery comprising:securing a bone spike in a distal end of a first bone in a joint of apatient; measuring resistance in soft tissues connected to the firstbone using a force sensor of a soft tissue balancing device coupled to adistal end of the bone spike via a spike socket; manipulating the softtissue balancing device during the soft tissue balancing test using arobotic arm; and outputting an indication of tension in the soft tissueduring a soft tissue balancing test.

In Example 48, the subject matter of Example 47 optionally includeswherein the first bone is a femur, and the soft tissue includesligaments connecting the femur to a tibia of the patient joint, andfurther comprising using the robotic arm is to manipulate the softtissue balancing device with the femur and the tibia in flexion orextension.

In Example 49, the subject matter of any one or more of Examples 47-48optionally include wherein manipulating the soft tissue balancing deviceincludes applying tension to the joint using the robotic arm through thesoft tissue balancing device during the soft tissue balancing test.

In Example 50, the subject matter of any one or more of Examples 47-49optionally include outputting, from the robotic arm, a resection anglefor an at least partial joint replacement to a computing device tocalculate soft tissue balance in the joint.

In Example 51, the subject matter of Example 50 optionally includescalculating, using the computing device, a pin placement location for acut guide based on the resection angle.

In Example 52, the subject matter of Example 51 optionally includespositioning, using the robotic arm, a pin placement trial for placing apin at a location on the first bone according to the pin placementlocation.

In Example 53, the subject matter of any one or more of Examples 47-52optionally include outputting, from a force sensor, force dataindicative of soft tissue tension in the patient joint when the force isapplied to the first bone by the soft tissue balancing component.

In Example 54, the subject matter of Example 53 optionally includesdetermining soft tissue tension at the patient joint based on the forcedata.

In Example 55, the subject matter of any one or more of Examples 47-54optionally include moving the robotic arm to a soft tissue balancingtest position and orientation relative to the first bone; controllingthe robotic arm to retain the position and orientation relative to thefirst bone when the bone moves; and applying a force to the first boneusing the soft tissue balancing component.

In Example 56, the subject matter of Example 55 optionally includestracking movement of the first bone using an optical tracking systemincluding a first optical tracker affixed to the first bone of thepatient and a second optical tracker affixed to the robotic arm; anddetermining the tension in the soft tissue during a soft tissuebalancing test using the tracked movement of the first bone.

In Example 57, the subject matter of Example 56 optionally includestracking a position and orientation of the soft tissue balancingcomponent when moved; and determining soft tissue tension using theposition and orientation of the end effector and information from theoptical tracking system including a position of the second opticaltracker affixed to the robotic arm and a position of the first opticaltracker affixed to the first bone.

In Example 58, the subject matter of Example 57 optionally includesdetermining a tension in medial soft tissue and a tension in lateralsoft tissue using a force vector of the soft tissue balancing componenton the first bone provided by the force sensor and a relative boneorientation of the first bone to a second bone provided by the opticaltracking system.

Example 59 is a robot-aided surgical system comprising: an end effectorof a robotic arm configured to apply a force to a tibia of a knee jointof a patient when the robotic arm is in contact with the tibia and movedin a specified direction to perform a soft tissue balancing test; and adisplay device to output an indication of tension in soft tissue duringthe soft tissue balancing test.

In Example 60, the subject matter of Example 59 optionally includes aforce sensor to output force data indicative of soft tissue tension inthe patient joint when the force is applied to the tibia by the roboticarm.

In Example 61, the subject matter of Example 60 optionally includes aprocessor to determine soft tissue tension at the patient joint based onthe force data.

In Example 62, the subject matter of any one or more of Examples 59-61optionally include an optical tracking system including a first opticaltracker affixed to the tibia of the patient, the optical tracking systemto track movement of the tibia.

In Example 63, the subject matter of Example 62 optionally includes arobotic controller to: move the end effector of the robotic arm to asoft tissue balancing test position and orientation relative to thetibia; control the robotic arm to retain the position and orientation ofthe end effector relative to the tibia when the optical tracking systemindicates movement of the tibia; and apply a force to the tibia usingthe robotic arm.

In Example 64, the subject matter of Example 63 optionally includes aprocessor to: track a position and orientation of the end effector whenmoved by the robotic controller; and determine soft tissue tension usingthe position and orientation Af the end effector and information fromthe optical tracking system including a position of the first opticaltracker affixed to the tibia.

In Example 65, the subject matter of any one or more of Examples 63-64optionally include a second optical tracker affixed to the robotic arm,and wherein the robotic controller is to use a position of the secondoptical tracker affixed to the robotic arm to determine the position andorientation of the end effector relative to the tibia.

In Example 66, the subject matter of any one or more of Examples 59-65optionally include a processor to enable a manual movement mode of therobotic arm, the manual movement mode allowing a surgeon to initiatemovement of the end effector of the robotic arm, the initiated movementcontinued by augmented force applied by the robotic arm.

In Example 67, the subject matter of Example 66 optionally includeswherein the initiated movement causes the end effector to be in contactwith the tibia.

In Example 68, the subject matter of any one or more of Examples 59-67optionally include a processor to receive an indication to initiate thesoft tissue balancing test, and in response, cause the robotic arm toinitiate the soft tissue balancing test.

In Example 69, the subject matter of any one or more of Examples 59-68optionally include a pin to couple the end effector to the tibia whenthe end effector is in contact with the tibia.

In Example 70, the subject matter of any one or more of Examples 59-69optionally include a processor to determine a resection angle on a cutof a femur connected via the soft tissue to the tibia based on theindication of tension in the soft tissue determined during the softtissue balancing test.

Example 71 is a tibial force detection system comprising: a tibialbaseplate including: a plurality of force sensors to detect forces atcorresponding locations of the tibial baseplate; and a plurality ofactuators corresponding to the plurality of force sensors, the pluralityof actuators causing the tibial baseplate to displace a femur from atibia at respective locations; and a processor to: receive forceinformation related to forces at the corresponding locations from theplurality of force sensors of the tibial baseplate; determine a rotationangle of the femur relative to the tibia based on the force information;and output the rotation angle for display.

In Example 72, the subject matter of Example 71 optionally includeswherein the plurality of force sensors include four force sensorscorresponding to four quadrants of the tibial baseplate.

In Example 73, the subject matter of any one or more of Examples 71-72optionally include wherein the plurality of actuators are configured tobe activated independently of each other.

In Example 74, the subject matter of any one or more of Examples 71-73optionally include wherein the plurality of actuators are activated toapply tension to one or more ligaments connecting the femur to the tibiauntil the one or more ligaments are in tension before determining therotation angle.

In Example 75, the subject matter of any one or more of Examples 71-74optionally include wherein the plurality of actuators include a numberof actuators corresponding to a number of force sensors of the pluralityof force sensors, and wherein the respective locations cause forces atthe corresponding locations of the tibial baseplate.

In Example 76, the subject matter of any one or more of Examples 71-75optionally include wherein the processor is further to use the rotationangle to determine a resection angle for a cut of the femur.

In Example 77, the subject matter of any one or more of Examples 71-76optionally include wherein in response to a release cut being performedon soft tissue connecting the femur to the tibia, the plurality ofactuators are further to cause the tibial baseplate to further displacethe femur from the tibia at respective locations.

In Example 78, the subject matter of any one or more of Examples 71-77optionally include wherein the plurality of actuators are to cause thetibial baseplate to release the femur from being displaced with respectto the tibia in response to the processor determining that the rotationangle is at a predetermined angle.

Example 79 is a method for performing a soft tissue pull test, themethod comprising: performing a soft tissue balancing test, using arobotic arm, while a joint connecting a femur to a tibia is inextension; inserting a soft tissue balancing component attached to adistal end of a robotic arm; performing the soft tissue balancing testusing the soft tissue balancing component and the robotic arm while thejoint is in flexion to determine a rotation to balance ligaments in thejoint; calculating pin placement for a cut guide based on the rotation;and placing the cut guide according to the pin placement using therobotic arm.

In Example 80, the subject matter of Example 79 optionally includesperforming a cut using the placed cut guide.

In Example 81, the subject matter of any one or more of Examples 79-80optionally include performing a tibial cut, using the robotic arm,before performing the soft tissue balancing test while the joint is inextension.

In Example 82, the subject matter of any one or more of Examples 79-81optionally include wherein calculating the pin placement includes usingsurgical planning software.

In Example 83, the subject matter of any one or more of Examples 79-82optionally include wherein the soft tissue balancing component is one ofa spike, a condyle pivot, or a j-shaped adapter.

Example 84 is a robotic arm controller comprising: a processor to:receive force data indicative of soft tissue tension in a patient jointduring movements of the patient joint by a robotic arm; receive trackingdata for the movements of the robotic arm; determine soft tissue tensionas a function of joint extension using the tracking data and the forcedata; and output the soft tissue tension as a function of jointextension.

In Example 85, the subject matter of Example 84 optionally includeswherein the processor is further to calculate a projected soft tissuetension as a function of joint extension using a model of at least oneimplant at a given location on a bone of the joint, and the actual softtissue tension as a function of joint extension, wherein the outputincludes the projected soft tissue tension as a function of jointextension.

In Example 86, the subject matter of Example 85 optionally includeswherein the processor is further to determine alterations required onthe bone to receive the at least one implant in the given location,using the model of the implant, wherein the output includes analteration file for operating a robotized apparatus in effecting thealterations.

In Example 87, the subject matter of any one or more of Examples 84-86optionally include wherein the processor is further to assesssoft-tissue balancing by calculating a rotation of bones of the jointsduring robot manipulations of the bone.

Example 88 is a CAS controller comprising: a tracking device forproducing tracking data representative of bone movements; arange-of-motion (ROM) analysis module configured for receiving trackingdata for the bone movements and for determining range of motion andjoint laxity data using said tracking data; a soft-tissue balancingmodule and an implant assessment module configured for updating jointlaxity data and calculating resection planes as a function of a model ofat least one implant at an adjustable location on a bone of the joint;and an output including the resection planes based on the adjustablelocation.

Example 89 is a robotic arm comprising: a tracking sensor to outputtracking data indicative of movement of the robotic arm, a soft tissuebalancing component affixed to an end effector at a distal end of therobotic arm, the soft tissue balancing component configured to apply aforce to a bone of a patient joint when the robotic arm is moved in aspecified direction; a force sensor to output force data indicative ofsoft tissue tension in the patient joint when the force is applied tothe bone by the soft tissue balancing component; and a processor to:determine soft tissue tension at the patient joint based on the trackingdata and the force data; and output the soft tissue tension.

In Example 90, the subject matter of Example 89 optionally includeswherein the soft tissue balancing component includes a spike.

In Example 91, the subject matter of any one or more of Examples 89-90optionally include wherein the soft tissue balancing component includesa condyle pivot.

In Example 92, the subject matter of any one or more of Examples 89-91optionally include wherein the soft tissue balancing component isaffixed to the robotic arm using a removable pin guide end effectorcomponent.

In Example 93, the subject matter of any one or more of Examples 89-92optionally include wherein the bone is a femur, and wherein the softtissue balancing component includes a ligament pulling componentconfigured to: snap in place on the end effector; and pull on the femurwith a patella in place.

In Example 94, the subject matter of Example 93 optionally includeswherein the processor is to: receive patella location information from asensor affixed to a back side of the patella; and output the patellalocation information during a range of motion test.

In Example 95, the subject matter of any one or more of Examples 89-94optionally include wherein the force is applied while the patient jointis in extension.

In Example 96, the subject matter of any one or more of Examples 89-95optionally include wherein the force is applied while the patient jointis in flexion.

In Example 97, the subject matter of any one or more of Examples 89-96optionally include wherein the robotic arm is controlled using a virtualcomponent displayed using an augmented reality device.

In Example 98, the subject matter of any one or more of Examples 89-97optionally include wherein the soft tissue tension is output to adisplay device to be displayed on a user interface.

In Example 99, the subject matter of Example 98 optionally includeswherein the user interface is to display varus and valgus angles of thepatient joint during a range of motion test.

Example 100 is a method of using a robotic arm to perform soft tissuebalancing, the method comprising: tracking, using a processor, movementof the robotic arm to obtain tracking data; applying a force, using asoft tissue balancing component coupled to a distal end of the roboticarm, to a bone of a patient joint; measuring the force to capture dataindicative of soft tissue tension in the patient joint when the force isapplied to the bone by the soft tissue balancing component; anddetermining soft tissue tension at the patient joint based on thetracking data and the force data; and outputting the soft tissuetension.

In Example 101, the subject matter of Example 100 optionally includeswherein the soft tissue balancing component includes a spike.

In Example 102, the subject matter of any one or more of Examples100-101 optionally include wherein the soft tissue balancing componentincludes a condyle pivot.

In Example 103, the subject matter of any one or more of Examples100-102 optionally include wherein the soft tissue balancing componentis affixed to the robotic arm using a removable pin guide end effectorcomponent.

In Example 104, the subject matter of any one or more of Examples100-103 optionally include wherein the bone is a femur, wherein the softtissue balancing component includes a ligament pulling component, andfurther comprising: snapping the ligament pulling component in place onthe end effector; and pulling, using the ligament pulling component onthe femur with a patella in place.

In Example 105, the subject matter of Example 104 optionally includesreceiving patella location information from a sensor affixed to a backside of the patella; and outputting the patella location informationduring a range of motion test.

In Example 106, the subject matter of any one or more of Examples100-105 optionally include wherein the force is applied while thepatient joint is in extension.

In Example 107, the subject matter of any one or more of Examples100-106 optionally include wherein the force is applied while thepatient joint is in flexion.

In Example 108, the subject matter of any one or more of Examples100-107 optionally include controlling the robotic arm using a virtualcomponent displayed using an augmented reality device.

In Example 109, the subject matter of any one or more of Examples100-108 optionally include wherein the soft tissue tension is output toa display device to be displayed on a user interface.

In Example 110, the subject matter of Example 109 optionally includeswherein the user interface is to display varus and valgus angles of thepatient joint during a range of motion test.

In Example 111, the subject matter of any one or more of Examples100-110 optionally include controlling the robotic arm to automaticallydetect a point on the bone; and registering the point as a landmarkusing the tracking data.

Example 112 is at least one non-transitory machine-readable mediumincluding instructions for operation of a robotic arm, which whenexecuted by at least one processor, cause the at least one processor toperform operations of any of the methods of Examples 100-111.

Example 113 is a tibial force detection system comprising: a tibialbaseplate including a plurality of force sensors to detect forces atcorresponding locations of the tibial baseplate; a processor to: receiveforce information for the corresponding locations from the plurality offorce sensors of the tibial baseplate; determine a rotation angle of afemur relative to a tibia based on the force information; and output therotation angle for display.

Example 114 is a robot-aided surgical system comprising elements of oneor more of Examples 1-113.

In Example 115, the subject matter of Example 114 optionally includesperforming a tibial cut, using the robotic arm, before performing thesoft tissue balancing test while the joint is in extension.

In Example 116, the subject matter of any one or more of Examples114-115 optionally include wherein the soft tissue balancing componentis one of a spike, a condyle pivot, or a j-shaped adapter.

In Example 117, the subject matter of any one or more of Examples114-116 optionally include wherein the processor is further to calculatea projected soft tissue tension as a function of joint extension using amodel of at least one implant at a given location on a bone of thejoint, and the actual soft tissue tension as a function of jointextension, wherein the output includes the projected soft tissue tensionas a function of joint extension.

In Example 118, the subject matter of Example 117 optionally includeswherein the processor is further to determine alterations required onthe bone to receive the at least one implant in the given location,using the model of the implant.

In Example 119, the subject matter of Example 118 optionally includeswherein the output includes an alteration file for operating a robotizedapparatus in effecting the alterations.

In Example 120, the subject matter of any one or more of Examples114-119 optionally include wherein the soft tissue balancing componentis affixed to the robotic arm using a removable pin guide end effectorcomponent.

In Example 121, the subject matter of any one or more of Examples114-120 optionally include wherein the soft tissue balancing componentincludes a j-shaped arm to couple to a femoral spike to allow forperformance of the soft tissue balancing test with a patella in place.

In Example 122, the subject matter of Example 121 optionally includeswherein the processor is to: receive patella location information from asensor affixed to a back side of the patella; and output the patellalocation information during a range of motion test.

In Example 123, the subject matter of any one or more of Examples114-122 optionally include wherein the robotic arm is controlled using avirtual component displayed using an augmented reality device.

In Example 124, the subject matter of any one or more of Examples114-123 optionally include wherein the soft tissue tension is output toa display device to be displayed on a user interface.

In Example 125, the subject matter of Example 124 optionally includeswherein the user interface is to display varus and valgus angles of thepatient joint during a range of motion test.

In Example 126, the subject matter of any one or more of Examples114-125 optionally include controlling the robotic arm to automaticallydetect a point on the bone; and registering the point as a landmarkusing the tracking data.

In Example 127, the subject matter of Example 126 optionally includesusing the landmark to determine the tension in the soft tissue during asoft tissue balancing test.

In Example 128, the subject matter of any one or more of Examples114-127 optionally include a removable holder, which when coupled to anend effector of the robotic arm, creates an anchor to receive a spike,the spike configured to couple the end effector to the bone.

In Example 129, the subject matter of any one or more of Examples114-128 optionally include an attachment to couple to an end effector ofthe robotic arm, the attachment comprising a spike, a J-hook, or anL-hook.

In Example 130, the subject matter of any one or more of Examples114-129 optionally include a spreader attached to a distal end of therobotic arm, the spreader configured to mechanically distract the firstbone from the second bone in the joint to perform the soft tissuebalancing test.

In Example 131, the subject matter of Example 130 optionally includeswherein the spreader includes a gear or a long lever arm to assist inmechanically distracting the first bone from the second bone.

In Example 132, the subject matter of any one or more of Examples114-131 optionally include a processor to determine whether the softtissue is in balance using information from a preoperative plan orimage.

In Example 133, the subject matter of any one or more of Examples114-132 optionally include wherein range of motion is testedpostoperatively to determine success of the soft tissue balancing test.

Example 134 is at least one non-transitory machine-readable mediumincluding instructions for operation of a robotic arm, which whenexecuted by at least one processor, cause the at least one processor toperform operations of any of the methods of Examples 1-133.

Example 135 is a method for performing any one of examples 1-133.

Method examples described herein may be machine or computer-implementedat least in part. Some examples may include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods may include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code may include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, in an example, the code may be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media may include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

1.-20. (canceled)
 21. A robot-aided surgical system comprising: aprocessor; a display device; and memory, including instructions, whichwhen executed by the processor, cause the processor to: receive anindication that a first surgical step has been completed on a patient bya robotic arm; identify an intermediate assessment for the patient;output for display, on a user interface of the display device,information related to the intermediate assessment; determine whetherthe intermediate assessment has been completed; and output for display,on the user interface in response to determining that the intermediateassessment has been completed, information corresponding to a secondsurgical step based on results of the intermediate assessment.
 22. Therobot-aided surgical system of claim 21, further comprising displayingthe indication on the user interface.
 23. The robot-aided surgicalsystem of claim 21, wherein the intermediate assessment includes a softtissue balancing test or an implant assessment.
 24. The robot-aidedsurgical system of claim 21, wherein displaying the informationcorresponding to the second surgical step includes displaying a bonemodel and an implant as a 3D representation, the 3D representationincluding selectable views including at least one of a flexion,extension, frontal plane, sagittal plane, or axial plane view.
 25. Therobot-aided surgical system of claim 21, wherein the informationcorresponding to the second surgical step includes a proposed implantmodel.
 26. The robot-aided surgical system of claim 21, furthercomprising: receiving a change to a planned implant model; and modifyinga displayed joint line based on the change.
 27. The robot-aided surgicalsystem of claim 21, wherein displaying the information related to theintermediate assessment includes displaying a gap distance, a currentfemur or tibia/valgus angle, or an anterior gap for patellofemoral jointstuffing.
 28. The robot-aided surgical system of claim 21, wherein thefirst surgical step includes a resection.
 29. The robot-aided surgicalsystem of claim 21, wherein the second surgical step is to be performedby the robotic arm.
 30. A robot-aided surgical method comprising:receiving, at a processor, an indication that a first surgical step hasbeen completed on a patient by a robotic arm; identifying anintermediate assessment for the patient; displaying, on a user interfaceof a display device, information related to the intermediate assessment;determining whether the intermediate assessment has been completed; anddisplaying, on the user interface in response to determining that theintermediate assessment has been completed, information corresponding toa second surgical step based on results of the intermediate assessment.31. The robot-aided surgical method of claim 30, further comprisingdisplaying the indication on the user interface.
 32. The robot-aidedsurgical method of claim 30, wherein the intermediate assessmentincludes a soft tissue balancing test or an implant assessment.
 33. Therobot-aided surgical method of claim 30, wherein displaying theinformation corresponding to the second surgical step includesdisplaying a bone model and an implant as a 3D representation, the 3Drepresentation including selectable views including at least one of aflexion, extension, frontal plane, sagittal plane, or axial plane view.34. The robot-aided surgical method of claim 30, wherein the informationcorresponding to the second surgical step includes a proposed implantmodel.
 35. The robot-aided surgical method of claim 30, furthercomprising: receiving a change to a planned implant model; and modifyinga displayed joint line based on the change.
 36. The robot-aided surgicalmethod of claim 30, wherein displaying the information related to theintermediate assessment includes displaying a gap distance, a currentfemur or tibia/valgus angle, or an anterior gap for patellofemoral jointstuffing.
 37. The robot-aided surgical method of claim 30, wherein thefirst surgical step includes a resection.
 38. The robot-aided surgicalmethod of claim 30, wherein the second surgical step is to be performedby the robotic arm.
 39. At least one non-transitory machine-readablemedium including instructions, which when executed by processingcircuitry, cause the processing circuitry to perform operations to;receive an indication that a first surgical step has been completed on apatient by a robotic arm; identify an intermediate assessment for thepatient; output for display, on a user interface of a display device,information related to the intermediate assessment; determine whetherthe intermediate assessment has been completed; and output for display,on the user interface in response to determining that the intermediateassessment has been completed, information corresponding to a secondsurgical step based on results of the intermediate assessment.
 40. Theat least one machine-readable medium of claim 39, wherein theintermediate assessment includes a soft tissue balancing test or animplant assessment.